22 (twenty-two) is the

natural number In mathematics, the natural numbers are the numbers 0, 1, 2, 3, and so on, possibly excluding 0. Some start counting with 0, defining the natural numbers as the non-negative integers , while others start with 1, defining them as the positive in ...

following 21 and preceding 23.

In mathematics

22 is a

semiprime In mathematics, a semiprime is a natural number that is the product of exactly two prime numbers. The two primes in the product may equal each other, so the semiprimes include the squares of prime numbers. Because there are infinitely many prime n ...

, a

Smith number In number theory, a Smith number is a composite number for which, in a given number base, the sum of its digits is equal to the sum of the digits in its prime factorization in the same base. In the case of numbers that are not square-free, the ...

, and an

Erdős–Woods number In number theory, a positive integer is said to be an Erdős–Woods number if it has the following property: there exists a positive integer such that in the sequence of consecutive integers, each of the elements has a non-trivial common fac ...

\frac = 3.14\ldots

is a commonly used

approximation An approximation is anything that is intentionally similar but not exactly equal to something else. Etymology and usage The word ''approximation'' is derived from Latin ''approximatus'', from ''proximus'' meaning ''very near'' and the prefix ...

of the

irrational number In mathematics, the irrational numbers are all the real numbers that are not rational numbers. That is, irrational numbers cannot be expressed as the ratio of two integers. When the ratio of lengths of two line segments is an irrational number, ...

, the ratio of the

circumference In geometry, the circumference () is the perimeter of a circle or ellipse. The circumference is the arc length of the circle, as if it were opened up and straightened out to a line segment. More generally, the perimeter is the curve length arou ...

of a circle to its

diameter In geometry, a diameter of a circle is any straight line segment that passes through the centre of the circle and whose endpoints lie on the circle. It can also be defined as the longest Chord (geometry), chord of the circle. Both definitions a ...

. 22 can read as "two twos", which is the only fixed point of John Conway's look-and-say function. The number 22 appears prominently within

sporadic groups In the mathematical classification of finite simple groups, there are a number of Group (mathematics), groups which do not fit into any infinite family. These are called the sporadic simple groups, or the sporadic finite groups, or just the spora ...

. The

Mathieu group In group theory, a topic in abstract algebra, the Mathieu groups are the five sporadic simple groups ''M''11, ''M''12, ''M''22, ''M''23 and ''M''24 introduced by . They are multiply transitive permutation groups on 11, 12, 22, 23 or 24 objec ...

M₂₂ is one of 26 sporadic

finite simple group In mathematics, the classification of finite simple groups states that every finite simple group is cyclic, or alternating, or in one of 16 families of groups of Lie type, or one of 26 sporadic groups. The list below gives all finite simple g ...

s, defined as the 3-transitive

permutation In mathematics, a permutation of a set can mean one of two different things: * an arrangement of its members in a sequence or linear order, or * the act or process of changing the linear order of an ordered set. An example of the first mean ...

representation on 22 points. There are also 22 regular complex apeirohedra. 22 has been proven to be a Lychrel number in base 2, since after 4 steps it reaches 10110100, after 8 steps it reaches 1011101000, after 12 steps it reaches 101111010000, and in general after steps it reaches a number consisting of 10, followed by ones, followed by 01, followed by zeros. This number obviously cannot be a palindrome, and none of the other numbers in the sequence are palindromes.

In other fields

*''

Catch-22 ''Catch-22'' is a satirical war novel by American author Joseph Heller. It was his debut novel. He began writing it in 1953; the novel was first published in 1961. Often cited as one of the most significant novels of the twentieth century, it ...

'' (1961),

Joseph Heller Joseph Heller (May 1, 1923 – December 12, 1999) was an American author of novels, short stories, plays, and screenplays. His best-known work is the 1961 novel '' Catch-22'', a satire on war and bureaucracy, whose title has become a synonym for ...

's novel, and its 1970 film adaptation gave rise to the expression of logic "

catch-22 ''Catch-22'' is a satirical war novel by American author Joseph Heller. It was his debut novel. He began writing it in 1953; the novel was first published in 1961. Often cited as one of the most significant novels of the twentieth century, it ...

". *

22 equal temperament In music, 22 equal temperament, called 22-TET, 22- EDO, or 22-ET, is the tempered scale derived by dividing the octave into 22 equal steps (equal frequency ratios). Each step represents a frequency ratio of , or 54.55 cents (). When composing wi ...

is a popular

microtonal Microtonality is the use in music of microtones — intervals smaller than a semitone, also called "microintervals". It may also be extended to include any music using intervals not found in the customary Western tuning of twelve equal interv ...

tuning temperament due to its good approximation of harmonic intervals, especially septimal intervals.

In culture and religion

*22 is a master number in

numerology Numerology (known before the 20th century as arithmancy) is the belief in an occult, divine or mystical relationship between a number and one or more coinciding events. It is also the study of the numerical value, via an alphanumeric system, ...

. *There are 22 colored properties on a traditional

Monopoly A monopoly (from Greek language, Greek and ) is a market in which one person or company is the only supplier of a particular good or service. A monopoly is characterized by a lack of economic Competition (economics), competition to produce ...

board.

In weights and measures

*The number of

yard The yard (symbol: yd) is an English units, English unit of length in both the British imperial units, imperial and US United States customary units, customary systems of measurement equalling 3 foot (unit), feet or 36 inches. Sinc ...

s in a

chain A chain is a serial assembly of connected pieces, called links, typically made of metal, with an overall character similar to that of a rope in that it is flexible and curved in compression but linear, rigid, and load-bearing in tension. A ...

In other uses

Twenty-two may also refer to: *In

French French may refer to: * Something of, from, or related to France ** French language, which originated in France ** French people, a nation and ethnic group ** French cuisine, cooking traditions and practices Arts and media * The French (band), ...

jargon, "22" is used as a phrase to warn of the coming of the police (typically ''"' !"'', in English: "5-0! Cops!") * In

Spanish lottery Spanish might refer to: * Items from or related to Spain: **Spaniards are a nation and ethnic group indigenous to Spain **Spanish language, spoken in Spain and many countries in the Americas **Spanish cuisine **Spanish history **Spanish culture ...

and

bingo Bingo or B-I-N-G-O may refer to: Arts and entertainment Gaming * Bingo, a game using a printed card of numbers ** Bingo (British version), a game using a printed card of 15 numbers on three lines; most commonly played in the UK and Ireland ** B ...

, 22 is nicknamed after its shape.

References

External links

* {{Integers, zero Integers