22 (number)

22 is a semiprime,^[1] a Smith number, and an Erdős–Woods number.^[2][3] ${\displaystyle {\frac {22}{7}}=3.14{\color {red}28}\ldots }$ is a commonly used approximation of the irrational number π, 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.^[4]

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.^[5] There are also 22 regular complex apeirohedra.^[6]

• There are 22 genetically encoded amino acids throughout known life that generate proteins during RNA translation.^[7]
• Catch-22 (1961), Joseph Heller's novel, and its 1970 film adaptation gave rise to the expression of logic "catch-22".^[8]
• 22 equal temperament is a popular microtonal tuning temperament due to its good approximation of harmonic intervals, especially septimal intervals.

• 22 is a master number in numerology.^[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.

• The number of yards in a chain.^[10]

Twenty-two may also refer to:

• In French jargon, "22" is used as a phrase to warn of the coming of the police (typically "22, v'là les flics !", in English: "5-0! Cops!")
• In Spanish lottery and bingo, 22 is nicknamed los dos patitos, 'the two little ducks' after its shape.^[11][12]

• Catch 22 (disambiguation)