281 (number)
{{Infobox number
| number = 281
| prime = 60th
}}
281 is the natural number following 280 and preceding 282. It is also a prime number.
In mathematics
281 is a twin prime with 283,{{Cite OEIS|A001359|name=Lesser of twin primes}} Sophie Germain prime,{{Cite OEIS|A005384|name=Sophie Germain primes p: 2p+1 is also prime}} sum of the first fourteen primes, sum of seven consecutive primes (29 + 31 + 37 + 41 + 43 + 47 + 53), Chen prime, {{Cite OEIS|A109611|chen prime}} Eisenstein prime with no imaginary part, and a centered decagonal number. {{Cite OEIS|A062786|centered 10-gonal numbers}}
281 is the smallest prime p such that the decimal period length of the reciprocal of p is (p−1)/10, i.e. the period length of 1/281 is 28. However, in binary, it has period length 70.
The generalized repunit number is composite for all prime p < 60000.