2000 (number)#2300 to 2399

{{see also|millennium|2000|Y2K (disambiguation){{!}}Y2K}}

{{Infobox number

| number = 2000

| unicode = MM, mm

|lang1=Armenian|lang1 symbol=Ս|lang3=Egyptian hieroglyph|lang3 symbol=𓆽}}

2000 (two thousand) is a natural number following 1999 and preceding 2001.

It is:

:*the highest number expressible using only two unmodified characters in Roman numerals (MM)

:*an Achilles number{{cite OEIS|A052486|name=Achilles numbers - powerful but imperfect: if n = Product(p_i^e_i) then all e_i > 1 (i.e., powerful), but the highest common factor of the e_i is 1, i.e., not a perfect power}}

:*smallest four digit eban number{{cite OEIS|A006933|'Eban' numbers (the letter 'e' is banned!)}}

:*the sum of all the nban numbers in the sequence{{cite OEIS|A008537|Numbers that do not contain the letter 'n')}}

Selected numbers in the range 2001–2999

=2001 to 2099=

2001 – sphenic number{{cite OEIS|A007304|Sphenic numbers: products of 3 distinct primes)}}
2002 = 7⁴ – 7³ – 7² – 7. Palindromic number in decimal, base 76, 90, 142, and 11 other non-trivial bases.
2003 – Sophie Germain prime and the smallest prime number in the 2000s
2004 – Area of the 24th [https://oeis.org/A022264/a022264.jpg crystagon]{{cite OEIS|A022264|n×(7×n - 1)/2}}
2005 – A vertically symmetric number
2006 – number of subsets of {1,2,3,4,5,6,7,8,9,10,11} with relatively prime elements{{cite OEIS|A085945|Number of subsets of {1,2,...,n} with relatively prime elements}}
2007 – 2²⁰⁰⁷ + 2007² is prime{{cite OEIS|A064539|Numbers n such that 2^n + n^2 is prime}}
2008 – number of 4 × 4 matrices with nonnegative integer entries and row and column sums equal to 3{{cite OEIS|A001496|Number of 4 × 4 matrices with nonnegative integer entries and row and column sums equal to n}}
2009 = 28² + 35², sum of two squares
2010 – number of compositions of 12 into relatively prime parts{{cite OEIS|A000740|Number of 2n-bead balanced binary necklaces of fundamental period 2n, equivalent to reversed complement}}
2011 – sexy prime with 2017, sum of eleven consecutive primes: 2011 = 157 + 163 + 167 + 173 + 179 + 181 + 191 + 193 + 197 + 199 + 211
2012 – The number 8 × 10²⁰¹² − 1 is a prime number{{cite OEIS|A056721|Numbers n such that 8×10^n-1 is prime}}
2013 – number of widely totally strongly normal compositions of 17
2014 – 5 × 2²⁰¹⁴ - 1 is prime{{cite OEIS|A001770|Numbers k such that 5×2^k - 1 is prime}}
2015 – Lucas–Carmichael number{{Cite OEIS|A006972|Lucas-Carmichael numbers}}
2016 – triangular number, number of 5-cubes in a 9-cube, Erdős–Nicolas number,{{Cite OEIS|A194472|Erdős-Nicolas numbers}} 2¹¹-2⁵
2017 – Mertens function zero, sexy prime with 2011
2018 – Number of partitions of 60 into prime parts
2019 – smallest number that can be represented as the sum of 3 prime squares 6 different ways: 2019 = 7² + 11² + 43² = 7² + 17² + 41² = 13² + 13² + 41² = 11² + 23² + 37² = 17² + 19² + 37² = 23² + 23² + 31²{{Cite web|date=2018-12-31|title=Can you solve it? 2019 in numbers|url=http://www.theguardian.com/science/2018/dec/31/can-you-solve-it-2019-in-numbers|access-date=2021-09-19|website=the Guardian|language=en}}
2020 – sum of the totient function for the first 81 integers
2021 = 43 × 47, consecutive prime numbers, next is 2491
2022 – non-isomorphic colorings of a toroidal 3 × 3 grid using exactly three colors under translational symmetry,{{cite OEIS|A294685|non-isomorphic colorings of a toroidal n × k grid using exactly three colors under translational symmetry}} beginning of a run of 4 consecutive Niven numbers{{cite OEIS|A141769|Beginning of a run of 4 consecutive Niven (or Harshad) numbers}}
2023 = 7 × 17² – multiple of 7 with digit sum equal to 7,{{cite OEIS|A063416|Multiples of 7 whose sum of digits is equal to 7}} sum of squares of digits equals 17
2024 – tetrahedral number{{Cite OEIS|A000292|Tetrahedral numbers}}
2025 = 45², square of the sum of the first nine positive integers (and therefore sum of the cubes of the first nine positive integers, by Nicomachus's theorem), centered octagonal number,{{Cite OEIS|1=A016754|2=Odd squares: a(n) = (2n+1)^2. Also centered octagonal numbers}} lowest number with exactly 15 odd divisors.{{Cite OEIS |A038547 |Least number with exactly n odd divisors. }} Sum of odd numbers from 1 to 89, current year.
2026 = Number of hyperforests spanning 10 unlabeled nodes without isolated vertices{{cite OEIS|A144959|A134955(n) - A134955(n-1). Number of hyperforests spanning n unlabeled nodes without isolated vertices.}}
2027 – super-prime, safe prime{{Cite OEIS|A005385|Safe primes}}
2028 = 13³ – 13²
2029 – member of the Mian–Chowla sequence{{Cite OEIS|A005282|Mian-Chowla sequence}}
2030 = 21² + 22² + 23² + 24² = 25² + 26² + 27²
2031 – centered pentagonal number{{Cite OEIS|A005891|Centered pentagonal numbers}}
2032 – number of binary Lyndon words of length 16 with an even number of 1's{{cite OEIS|A051841|Number of binary Lyndon words with an even number of 1's}}
2033 - number of rooted trees with 9 nodes and a single labeled node{{cite OEIS|A000107|Number of rooted trees with n nodes and a single labeled node; pointed rooted trees; vertebrates}}
2034 - number of unlabeled graphs on 11 nodes whose components are unicyclic graphs{{cite OEIS|A137917|number of unlabeled graphs on n nodes whose components are unicyclic graphs}}
2035 – Wolstenholme number{{cite OEIS|A007408|Wolstenholme numbers}}
2036 – Eulerian number{{cite OEIS|A000295|Eulerian numbers}}
2037 = 2¹¹ - 11{{cite OEIS|A000325|2^n - n}}
2038 – Number of unlabeled Euler graphs with 9 nodes{{cite OEIS|A002854|Number of unlabeled Euler graphs with n nodes; number of unlabeled two-graphs with n nodes; number of unlabeled switching classes of graphs with n nodes; number of switching classes of unlabeled signed complete graphs on n nodes; number of Seidel matrices of order n}}
2039 – Sophie Germain prime, safe prime
2040 = $\frac{15 \times 16 \times 17}{2}$ {{cite OEIS|A027480|n*(n+1)*(n+2)/2}}
2045 – number of partially ordered set with 7 unlabeled elements{{cite OEIS|A000112|Number of partially ordered sets (posets) with n unlabeled elements}}
2047 – super-Poulet number,{{Cite OEIS|A050217|Super-Poulet numbers}} Woodall number,{{Cite OEIS|A003261|Woodall numbers}} decagonal number,{{Cite OEIS|A001107|10-gonal (or decagonal) numbers}} a centered octahedral number,{{cite OEIS|A001845|Centered octahedral numbers (crystal ball sequence for cubic lattice)}} 2047 = 2¹¹ - 1 = 23 × 89 and is the first Mersenne number that is composite for a prime exponent
2048 = 2¹¹
2050 – sum of 2 consecutive odd squares (31² + 33²)
2053 – star number
2056 – magic constant of n × n normal magic square and n-queens problem for n = 16
2060 – sum of the totient function for the first 82 integers
2063 – Sophie Germain prime, safe prime, super-prime
2068 – number of 16-bead binary necklaces with beads of 2 colors where the colors may be swapped but turning over is not allowed{{cite OEIS|A000013|Definition (1): Number of n-bead binary necklaces with beads of 2 colors where the colors may be swapped but turning over is not allowed}}
2069 – Sophie Germain prime
2070 – pronic number{{Cite OEIS|A002378|Oblong (or promic, pronic, or heteromecic) numbers}}
2080 – triangular number
2081 – super-prime
2093 – Mertens function zero
2095 – Mertens function zero
2096 – Mertens function zero
2097 – Mertens function zero
2099 – Mertens function zero, super-prime, safe prime, highly cototient number{{Cite OEIS|A100827|Highly cototient numbers}}

=2100 to 2199=

2100 – Mertens function zero
2101 – centered heptagonal number{{Cite OEIS|1=A069099|2=Centered heptagonal numbers|access-date=2016-06-13}}
2107 – member of a Ruth–Aaron pair with 2108 (first definition)
2108 – member of a Ruth–Aaron pair with 2107 (first definition)
2109 – square pyramidal number,{{Cite OEIS|1=A000330|2=Square pyramidal numbers|access-date=2016-06-13}} the sum of the third and last trio of three-digit permutable primes in decimal: 199 + 919 + 991
2112 – The break-through album of the band Rush
2113 – Mertens function zero, Proth prime,{{Cite OEIS|1=A080076|2=Proth primes|access-date=2016-06-13}} centered square number{{Cite OEIS|1=A001844|2=Centered square numbers|access-date=2016-06-13}}
2116 = 46²
2117 – Mertens function zero
2119 – Mertens function zero
2120 – Mertens function zero, Fine number{{cite OEIS|A000957|2=Fine's sequence (or Fine numbers): number of relations of valence >= 1 on an n-set; also number of ordered rooted trees with n edges having root of even degree}}
2122 – Mertens function zero
2125 – nonagonal number{{Cite OEIS|1=A001106|2=9-gonal (or enneagonal or nonagonal) numbers|access-date=2016-06-13}}
2127 – sum of the first 34 primes
2129 – Sophie Germain prime
2135 – Mertens function zero
2136 – Mertens function zero
2137 – prime of the form 2p-1
2138 – Mertens function zero
2141 – Sophie Germain prime
2142 – sum of the totient function for the first 83 integers
2143 – almost exactly 22{{pi}}⁴
2145 – triangular number
2153 – with 2161, smallest consecutive primes that have the same sum of digits as each other's prime indices
2160 – largely composite number{{Cite OEIS|A067128|Ramanujan's largely composite numbers}}
2161 – with 2153, smallest consecutive primes that have the same sum of digits as each other's prime indices
2162 – pronic number
2166 – sum of the totient function for the first 84 integers
2169 – Leyland number{{Cite OEIS|1=A076980|2=Leyland numbers|access-date=2016-06-13}}
2171 – Mertens function zero
2172 – Mertens function zero
2175 – smallest number requiring 143 seventh powers for Waring representation
2176 – pentagonal pyramidal number,{{Cite OEIS|1=A002411|2=Pentagonal pyramidal numbers|access-date=2016-06-13}} centered pentagonal number, number of prime knots with 12 crossings
2178 – first natural number whose digits in its decimal representation get reversed when multiplied by 4{{Cite OEIS|1=A008918|2=Numbers n such that 4*n = (n written backwards)|access-date=2016-06-14}}
2179 – Wedderburn–Etherington prime{{Cite OEIS|1=A001190|2=Wedderburn-Etherington numbers|access-date=2016-06-13}}
2184 – equals both 3⁷ − 3 and 13³ − 13 and is believed to be the only such doubly strictly absurd number{{cite journal

| last = Mackenzie

| first = Dana

| title = 2184: An Absurd (and Adsurd) Tale

| url = http://math.colgate.edu/~integers/s33/s33.Abstract.html

| journal = Integers

| volume = 18

| year = 2018

}}{{Unreliable source?|date=July 2019}}

2187 = 3⁷, vampire number,{{Cite OEIS|1=A014575|2=Vampire numbers|access-date=2016-06-13}} perfect totient number{{Cite OEIS|1=A082897|2=Perfect totient numbers|access-date=2016-06-13}}
2188 – Motzkin number{{Cite OEIS|1=A001006|2=Motzkin numbers|access-date=2016-06-13}}
2197 = 13³, palindromic in base 12 (1331₁₂)
2199 – perfect totient number

=2200 to 2299=

2201 – only known non-palindromic number whose cube is palindromic; also no known fourth or higher powers are palindromic for non-palindromic numbers
2203 – Mersenne prime exponent
2205 – odd abundant number{{Cite OEIS|1=A005231|2=Odd abundant numbers|access-date=2016-06-13}}
2207 – safe prime, Lucas prime{{Cite OEIS|1=A005479|2=Prime Lucas numbers|access-date=2016-06-13}}
2208 – Keith number{{Cite OEIS|1=A007629|2=Repfigit (REPetitive FIbonacci-like diGIT) numbers (or Keith numbers)|access-date=2016-06-13}}
2209 = 47², palindromic in base 14 (B3B₁₄), centered octagonal number
2211 – triangular number
2221 – super-prime, happy number
2222 – repdigit
2223 – Kaprekar number{{Cite OEIS|1=A006886|2=Kaprekar numbers|access-date=2016-06-13}}
2230 – sum of the totient function for the first 85 integers
2232 – decagonal number
2236 – Harshad number
2245 – centered square number
2254 – member of the Mian–Chowla sequence
2255 – octahedral number{{Cite OEIS|1=A005900|2=Octahedral numbers|access-date=2016-06-13}}
2256 – pronic number
2269 – super-prime, cuban prime{{Cite OEIS|1=A002407|2=Cuban primes|access-date=2016-06-13}}
2272 – sum of the totient function for the first 86 integers
2273 – Sophie Germain prime
2276 – sum of the first 35 primes, centered heptagonal number
2278 – triangular number
2281 – star number, Mersenne prime exponent
2287 – balanced prime{{Cite OEIS|1=A006562|2=Balanced primes|access-date=2016-06-13}}
2294 – Mertens function zero
2295 – Mertens function zero
2296 – Mertens function zero
2299 – member of a Ruth–Aaron pair with 2300 (first definition)

=2300 to 2399=

2300 – tetrahedral number, member of a Ruth–Aaron pair with 2299 (first definition)
2301 – nonagonal number
2304 = 48²
2306 – Mertens function zero
2309 – primorial prime, twin prime with 2311, Mertens function zero, highly cototient number
2310 – fifth primorial{{Cite OEIS|1=A002110|2=Primorial numbers|access-date=2016-06-13}}
2311 – primorial prime, twin prime with 2309
2321 – Mertens function zero
2322 – Mertens function zero
2326 – centered pentagonal number
2328 – sum of the totient function for the first 87 integers, the number of groups of order 128{{cite web|url=http://www-public.tu-bs.de:8080/~beick/soft/small/small.html |title=The Small Groups library |access-date=2008-01-22 |url-status=dead |archive-url=https://web.archive.org/web/20070204070922/http://www-public.tu-bs.de:8080/~beick/soft/small/small.html |archive-date=2007-02-04 }}.
2331 – centered cube number{{Cite OEIS|1=A005898|2=Centered cube numbers|access-date=2016-06-13}}
2338 – Mertens function zero
2339 – Sophie Germain prime, twin prime with 2341
2341 – super-prime, twin prime with 2339
2346 – triangular number
2347 – sum of seven consecutive primes (313 + 317 + 331 + 337 + 347 + 349 + 353)
2351 – Sophie Germain prime, super-prime
2352 – pronic number
2357 – Smarandache–Wellin prime{{Cite OEIS|1=A069151|2=Concatenations of consecutive primes, starting with 2, that are also prime|access-date=2016-06-13}}
2368 – sum of the totient function for the first 88 integers
2372 – logarithmic number{{cite OEIS|A002104|Logarithmic numbers}}
2378 – Pell number{{Cite OEIS|1=A000129|2=Pell numbers|access-date=2016-06-13}}
2379 – member of the Mian–Chowla sequence
2381 – super-prime, centered square number
2383 (2384) – number of delegates required to win the 2016 Democratic Party presidential primaries (out of 4051)
2393 – Sophie Germain prime
2397 – sum of the squares of the first ten primes
2399 – Sophie Germain prime

=2400 to 2499=

2400 – perfect score on SAT tests administered after 2005
2401 = 49² = 7⁴, centered octagonal number
2415 – triangular number
2417 – super-prime, balanced prime
2425 – decagonal number
2427 – sum of the first 36 primes
2431 – product of three consecutive primes
2437 – cuban prime, largest right-truncatable prime in base 5
2447 – safe prime
2450 – pronic number
2456 – sum of the totient function for the first 89 integers
2458 – centered heptagonal number
2459 – Sophie Germain prime, safe prime
2465 – magic constant of n × n normal magic square and n-queens problem for n = 17, Carmichael number{{Cite OEIS|1=A002997|2=Carmichael numbers|access-date=2016-06-13}}
2470 – square pyramidal number
2471 – number of ways to partition {1,2,3,4,5,6} and then partition each cell (block) into subcells{{cite OEIS|A000258|Expansion of e.g.f. exp(exp(exp(x)-1)-1)}}
2477 – super-prime, cousin prime
2480 – sum of the totient function for the first 90 integers
2481 – centered pentagonal number
2484 – nonagonal number
2485 – triangular number, number of planar partitions of 13{{cite OEIS|A000219|Number of planar partitions (or plane partitions) of n}}
2491 = 47 * 53, consecutive prime numbers, member of Ruth–Aaron pair with 2492 under second definition
2492 – member of Ruth–Aaron pair with 2491 under second definition

=2500 to 2599=

2500 = 50², palindromic in base 7 (10201₇)
2501 – Mertens function zero
2502 – Mertens function zero
2503 – Friedman prime
2510 – member of the Mian–Chowla sequence
2513 – member of the Padovan sequence{{Cite OEIS|1=A000931|2=Padovan sequence|access-date=2016-06-13}}
2517 – Mertens function zero
2519 – the smallest number congruent to 1 (mod 2), 2 (mod 3), 3 (mod 4), ..., 9 (mod 10)
2520 – superior highly composite number; smallest number divisible by numbers 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, and 12; colossally abundant number; Harshad number in several bases. It is also the highest number with more divisors than any number less than double itself {{OEIS|id=A072938}}. Not only it is the 7th (and last) number with more divisors than any number double itself but is also the 7th number that is highly composite and the lowest common multiple of a consecutive set of integers from 1 {{OEIS|id=A095921}} which is a property the previous number with this pattern of divisors does not have (360). That is, although 360 and 2520 both have more divisors than any number twice themselves, 2520 is the lowest number divisible by both 1 to 9 and 1 to 10, whereas 360 is not the lowest number divisible by 1 to 6 (which 60 is) and is not divisible by 1 to 7 (which 420 is). It is also the 6th and largest highly composite number that is a divisor of every higher highly composite number {{OEIS|id=A106037}}.
2521 – star prime, centered square number
2522 – Mertens function zero
2523 – Mertens function zero
2524 – Mertens function zero
2525 – Mertens function zero
2530 – Mertens function zero, Leyland number
2533 – Mertens function zero
2537 – Mertens function zero
2538 – Mertens function zero
2543 – Sophie Germain prime, sexy prime with 2549
2548 = 14³ - 14²
2549 – Sophie Germain prime, super-prime, sexy prime with 2543
2550 – pronic number
2552 – sum of the totient function for the first 91 integers
2556 – triangular number
2567 – Mertens function zero
2568 – Mertens function zero, number of digits in the decimal expansion of 1000!, or the product of all natural numbers from 1 to 1000
2570 – Mertens function zero
2579 – safe prime
2580 – Keith number, forms a column on a telephone or PIN pad
2584 – Fibonacci number,{{Cite OEIS|1=A000045|2=Fibonacci numbers|access-date=2016-06-13}} sum of the first 37 primes
2592 – 3-smooth number (2⁵×3⁴)
2596 – sum of the totient function for the first 92 integers

=2600 to 2699=

2600 – tetrahedral number, member of a Ruth–Aaron pair with 2601 (first definition)
2600 Hz is the tone used by a blue box to defeat toll charges on long distance telephone calls
2600: The Hacker Quarterly is a magazine named after the above
The Atari 2600 was a popular video game console
2601 = 51², member of a Ruth–Aaron pair with 2600 (first definition)
2609 – super-prime
2620 – telephone number, amicable number with 2924
2625 = a centered octahedral number
2626 – decagonal number
2628 – triangular number
2632 – number of consecutive baseball games played by Cal Ripken Jr.
2633 – sum of twenty-five consecutive primes (47 + 53 + 59 + 61 + 67 + 71 + 73 + 79 + 83 + 89 + 97 + 101 + 103 + 107 + 109 + 113 + 127 + 131 + 137 + 139 + 149 + 151 + 157 + 163 + 167)
2641 – centered pentagonal number
2647 – super-prime, centered heptagonal number
2652 – pronic number
2656 – sum of the totient function for the first 93 integers
2665 – centered square number
2674 – nonagonal number
2677 – balanced prime
2680 – number of 11-queens problem solutions
2683 – super-prime
2689 – Mertens function zero, Proth prime
2693 – Sophie Germain prime
2699 – Sophie Germain prime

=2700 to 2799=

2701 – triangular number, super-Poulet number
2702 – sum of the totient function for the first 94 integers
2704 = 52²
2707 – strong prime, model number for the concept supersonic airliner Boeing 2707
{{Vanchor|2719}} – super-prime, largest known odd number which cannot be expressed in the form x² + y² + 10z² where x, y and z are integers.{{cite encyclopedia|title=Odd numbers that are not of the form x^2+y^2+10*z^2.|url=http://oeis.org/search?q=3%2C+7%2C+21%2C+31%2C+33%2C+43%2C&language=english&go=Search|encyclopedia=The Online Encyclopedia of Integer Sequences|publisher=The OEIS Foundation, Inc.|access-date=13 November 2012}} In 1997 it was conjectured that this is also the largest such odd number.{{cite journal|last=Ono|first=Ken|title=Ramanujan, taxicabs, birthdates, zipcodes and twists|journal=American Mathematical Monthly|year=1997|volume=104|issue=10|pages=912–917|url=http://www.mathcs.emory.edu/~ono/publications-cv/pdfs/023.pdf|access-date=11 November 2012|doi=10.2307/2974471|jstor=2974471|citeseerx=10.1.1.514.8070|archive-date=15 October 2015|archive-url=https://web.archive.org/web/20151015193211/http://www.mathcs.emory.edu/~ono/publications-cv/pdfs/023.pdf|url-status=dead}} It is now{{When|date=April 2024|reason=When is "now"?}} known this is true if the generalized Riemann hypothesis is true.{{cite journal|last=Ono|first=Ken|author2=K Soundararajan|title=Ramanujan's ternary quadratic forms|journal=Inventiones Mathematicae|year=1997|volume=130|issue=3|pages=415–454|url=http://mathcs.emory.edu/~ono/publications-cv/pdfs/025.pdf|access-date=12 November 2012|doi=10.1007/s002220050191|bibcode=1997InMat.130..415O|citeseerx=10.1.1.585.8840|s2cid=122314044|archive-url=https://web.archive.org/web/20190718155256/http://www.mathcs.emory.edu/~ono/publications-cv/pdfs/025.pdf|archive-date=18 July 2019|url-status=dead}}
2728 – Kaprekar number
2729 – highly cototient number
2731 – the only Wagstaff prime with four digits,{{Cite OEIS|1=A000979|2=Wagstaff primes|access-date=2016-06-13}} Jacobsthal prime
2736 – octahedral number
2741 – Sophie Germain prime, 400th prime number
2744 = 14³, palindromic in base 13 (1331₁₃)
2747 – sum of the first 38 primes
2749 – super-prime, cousin prime with 2753
2753 – Sophie Germain prime, Proth prime
2756 – pronic number
2763 - Factors of 2763 are 1, 3, 9, 307, 921. There are 5 integers that are factors of 2763. The biggest factor of 2763 is 921.
2774 – sum of the totient function for the first 95 integers
2775 – triangular number
2780 – member of the Mian–Chowla sequence
2783 – member of a Ruth–Aaron pair with 2784 (first definition)
2784 – member of a Ruth–Aaron pair with 2783 (first definition)
2791 – cuban prime

=2800 to 2899=

2801 – first base 7 repunit prime
2803 – super-prime
2806 – centered pentagonal number, sum of the totient function for the first 96 integers
2809 = 53², centered octagonal number
2813 – centered square number
2816 – number of parts in all compositions of 10{{cite OEIS|A001792|2=a(n) = (n+2)*2^(n-1)}}
2819 – Sophie Germain prime, safe prime, sum of seven consecutive primes (383 + 389 + 397 + 401 + 409 + 419 + 421)
2821 – Carmichael number
2835 – odd abundant number, decagonal number
2843 – centered heptagonal prime{{Cite OEIS|1=A144974|2=Centered heptagonal prime numbers|access-date=2016-06-13}}
2850 – triangular number
2862 – pronic number
2870 – square pyramidal number
2871 – nonagonal number
2872 – tetranacci number{{Cite OEIS|1=A000078|2=Tetranacci numbers|access-date=2016-06-13}}
2875 — number of lines on a quintic threefold{{Citation | last1=Pandharipande | first1=Rahul | title=Rational curves on hypersurfaces (after A. Givental) | url=http://www.numdam.org/item?id=SB_1997-1998__40__307_0 | mr=1685628 | year=1998 | journal=Astérisque |volume=1997/98 |issue=252 | pages=307–340| arxiv=math/9806133 | bibcode=1998math......6133P }}
2879 – safe prime
2897 – super-prime, Markov prime{{Cite OEIS|1=A002559|2=Markoff (or Markov) numbers|access-date=2016-06-13}}

=2900 to 2999=

2902 – sum of the totient function for the first 97 integers
2903 – Sophie Germain prime, safe prime, balanced prime
2909 – super-prime
2914 – sum of the first 39 primes
2915 – Lucas–Carmichael number
2916 = 54²
2924 – amicable number with 2620
2925 – magic constant of n × n normal magic square and n-queens problem for n = 18, tetrahedral number, member of the Mian-Chowla sequence
2926 – triangular number
2939 – Sophie Germain prime
2944 – sum of the totient function for the first 98 integers
2963 – Sophie Germain prime, safe prime, balanced prime
2964 – number of parallelogram polyominoes with 11 cells{{cite OEIS|A006958|Number of parallelogram polyominoes with n cells (also called staircase polyominoes, although that term is overused)}}
2965 – greater of second pair of Smith brothers, centered square number
2969 – Sophie Germain prime
2970 – harmonic divisor number,{{Cite OEIS|1=A001599|2=Harmonic or Ore numbers|access-date=2016-06-13}} pronic number
2976 – centered pentagonal number
2988 – number of reduced trees with 20 nodes{{cite OEIS|A000014|Number of series-reduced trees with n nodes}}
2989 – in hexadecimal, reads as "BAD"
2997 – 1000-gonal number{{Cite OEIS|1=A195163|2=1000-gonal numbers|access-date=2016-06-13}}
2999 – safe prime

=Prime numbers=

There are 127 prime numbers between 2000 and 3000:{{Cite OEIS|A038823|Number of primes between n*1000 and (n+1)*1000}}{{cite web |last=Stein |first=William A. |author-link=William A. Stein |title=The Riemann Hypothesis and The Birch and Swinnerton-Dyer Conjecture |url=https://wstein.org/talks/2017-02-10-wing-rh_and_bsd/ |website=wstein.org |date=10 February 2017 |access-date=6 February 2021}}

:2003, 2011, 2017, 2027, 2029, 2039, 2053, 2063, 2069, 2081, 2083, 2087, 2089, 2099, 2111, 2113, 2129, 2131, 2137, 2141, 2143, 2153, 2161, 2179, 2203, 2207, 2213, 2221, 2237, 2239, 2243, 2251, 2267, 2269, 2273, 2281, 2287, 2293, 2297, 2309, 2311, 2333, 2339, 2341, 2347, 2351, 2357, 2371, 2377, 2381, 2383, 2389, 2393, 2399, 2411, 2417, 2423, 2437, 2441, 2447, 2459, 2467, 2473, 2477, 2503, 2521, 2531, 2539, 2543, 2549, 2551, 2557, 2579, 2591, 2593, 2609, 2617, 2621, 2633, 2647, 2657, 2659, 2663, 2671, 2677, 2683, 2687, 2689, 2693, 2699, 2707, 2711, 2713, 2719, 2729, 2731, 2741, 2749, 2753, 2767, 2777, 2789, 2791, 2797, 2801, 2803, 2819, 2833, 2837, 2843, 2851, 2857, 2861, 2879, 2887, 2897, 2903, 2909, 2917, 2927, 2939, 2953, 2957, 2963, 2969, 2971, 2999

References

Category:Integers