22 (number)
{{Infobox number
| number = 22
| divisor = 1, 2, 11, 22
}}
22 (twenty-two) is the natural number following 21 and preceding 23.
In mathematics
22 is a semiprime,{{Cite OEIS|sequencenumber=A001358}} a Smith number, and an Erdős–Woods number.{{Cite OEIS|A006753|Smith numbers|access-date=2016-05-31}}{{Cite OEIS|A059756|Erdős-Woods numbers|access-date=2016-05-31}} is a commonly used approximation of the irrational number {{pi}}, the ratio of the circumference of a circle to its diameter.
22 can read as "two twos", which is the only fixed point of John Conway's look-and-say function.{{Cite OEIS|A010861|Look-and-say constant sequence 22|access-date=2022-07-21}}
The number 22 appears prominently within sporadic groups. The Mathieu group M22 is one of 26 sporadic finite simple groups, defined as the 3-transitive permutation representation on 22 points.{{Cite web |last=Weisstein |first=Eric W. |title=Mathieu Groups |url=https://mathworld.wolfram.com/MathieuGroups.html |access-date=2022-07-02 |website=mathworld.wolfram.com |language=en}} There are also 22 regular complex apeirohedra.{{Citation |last=Coxeter |first=H.S.M. |title=Regular Complex Polytopes |page=140 |year=1991 |publisher=Cambridge University Press |isbn=0-521-39490-2 |authorlink=Harold Scott MacDonald Coxeter}}
22 has been proven to be a Lychrel number in base 2,{{Cite OEIS|A060382}} since after 4 steps it reaches 10110100, after 8 steps it reaches 1011101000, after 12 steps it reaches 101111010000, and in general after {{math|4n}} steps it reaches a number consisting of 10, followed by {{math|n + 1}} ones, followed by 01, followed by {{math|n + 1}} zeros. This number obviously cannot be a palindrome, and none of the other numbers in the sequence are palindromes.
In other fields
- Catch-22 (1961), Joseph Heller's novel, and its 1970 film adaptation gave rise to the expression of logic "catch-22".{{Cite web|title=Definition of CATCH-22|url=https://www.merriam-webster.com/dictionary/catch-22|access-date=2020-08-12|website=www.merriam-webster.com|language=en}}
- 22 equal temperament is a popular microtonal tuning temperament due to its good approximation of harmonic intervals, especially septimal intervals.
In culture and religion
- 22 is a master number in numerology.{{Cite book |last=Sharp |first=Damian |title=Simple Numerology: A Simple Wisdom book (A Simple Wisdom Book series) |publisher=Red Wheel |year=2001 |page=7 |language=English |isbn=978-1-57324-560-9 }}
- There are 22 colored properties on a traditional Monopoly board.
- There are 22 cards in the Major Arcana suit of a traditional tarot card deck, though they are often numbered 0-21.
In weights and measures
In other uses
Twenty-two may also refer to:
- In French jargon, "22" is used as a phrase to warn of the coming of the police (typically "{{Lang|fr|22, v'là les flics}} !", in English: "5-0! Cops!")
- In Spanish lottery and bingo, 22 is nicknamed {{Langx|es|los dos patitos|lit=the two little ducks|label=none}} after its shape.{{Cite news |last1=Cuartas |first1=Javier |title=La suerte de los dos patitos |url=https://elpais.com/diario/1990/01/06/agenda/631580402_850215.html |access-date=17 September 2020 |work=El País |date=1990-01-05 |location=Oviedo |language=es
See also
References
External links
{{Commons category}}
- {{Cite web|url=http://www.virtuescience.com/22.html|website=Virtuescience|title= The Number 22 at The Database of Number Correlations}}
{{Integers|zero}}