22 (number)

 ← 21 22 23 →
Cardinal twenty-two
Ordinal 22nd
(twenty-second)
Factorization 2 × 11
Divisors 1, 2, 11, 22
Roman numeral XXII
Binary 101102
Ternary 2113
Quaternary 1124
Quinary 425
Senary 346
Octal 268
Duodecimal 1A12
Vigesimal 1220
Base 36 M36

22 (twenty-two) is the natural number following 21 and preceding 23.

In mathematics

Twenty-two is an even composite number, its proper divisors being 1, 2 and 11. 22 is the sixth discrete semiprime and the fourth in the (2.q) family. With 21 it forms the second discrete semiprime pair. 22 has an aliquot sum of 14 and is the fifth composite number found in the 7-aliquot tree. It has a 7- member aliquot sequence 22, 14, 10, 8, 7, 1, 0 of which the next two members are themselves discrete semiprimes, 22 is the first discrete semiprime exhibiting this property. 169 also has 14 as its aliquot sum. 22 is itself the aliquot sum of two numbers 20, 38.

Twenty-two is a pentagonal number and a centered heptagonal number. When cutting a circle with just six line segments, the maximum number of pieces that can be so created is 22,[1] thus 22 is a central polygonal number (see lazy caterer's sequence).

The sum of the totient function for the first eight integers is 22. 22 is a Perrin number, preceded in the sequence by 10, 12, 17.

22 divided by 7 approximates the irrational number π, the ratio of the circumference of a circle to its diameter.

Since it is possible to find sequences of 22 consecutive integers such that each inner member shares a factor with either the first or the last member, 22 is an Erdős–Woods number.

It is a Smith number in base 10.

In playing cards

• Traditional Tarot decks have 22 cards with allegorical subjects. These serve as trump cards in the game. The Fool is usually a kind of wild-card among the trumps and unnumbered, so the highest trump is numbered 21. Occult Tarot decks usually have 22 similar cards which are called Major Arcana by fortune-tellers. Occultists have related this number to the 22 letters of the Hebrew alphabet and the 22 paths in the Kabbalistic Tree of Life.

In music

• The name of a song by punk band Millencolin.
• In Jay-Z's song "22 Two's", he rhymes the words: too, to and two, 22 times in the first verse.
• Iron Maiden has a song named "22 Acacia Avenue".
• Death Metal band Hypocrisy album "Catch 22" released in year 2002.
• Lily Allen has a song titled "22" from her album It's Not Me, It's You.
• Paul Weller has a song and album named 22 Dreams. The album contains 22 songs on it, including the song "22 Dreams".
• The Norwegian electronica project Ugress uses 22 as a recurring theme. All four albums features a track with 22 in the title.
• Taylor Swift has a song from her fourth album Red titled "22".

In jargon

• In French, "22" is used as a phrase to warn of the coming of the police (typically "22, v'là les flics !", "22, here come the cops!")

In other fields

Twenty-two may also refer to: