24 (number)

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24 (twenty-four) is the natural number following 23 and preceding 25. In English, it is the smallest integer with ten letters in its spelled out name.

The SI prefix for 1024 is yotta (Y), and for 10-24 (i.e., the reciprocal of 1024) yocto (y). These numbers are the largest and smallest number to receive an SI prefix to date.

<< 20 21 22 23 24 25 26 27 28 29 >>

Cardinal 24
twenty-four
Ordinal 24th
twenty-fourth
Factorization<math>2^3 \cdot 3</math>
Roman numeralXXIV
Binary11000
Hexadecimal18

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In mathematics

It is the factorial of 4 and a composite number, the smallest number with exactly eight divisors, its proper divisors being 1, 2, 3, 4, 6, 8, and 12, making it a highly composite number. Subtracting one from each of its divisors (except 1 and 2, but including itself) yields a prime number; 24 is the largest number with this property.

There are 10 solutions to the equation φ(x) = 24, namely 35, 39, 45, 52, 56, 70, 72, 78, 84 and 90. This is more than any integer below 24, making 24 a highly totient number.

24 is a nonagonal number. This number is also the sum of a twin prime (11 + 13). It is a Harshad number and a semi-meandric number.

24 is one of the few numbers for which the sum of <math>\mu(d)d^2</math> for each of its divisors is equal to itself. (This it has in common with 1).

In 24 dimensions there are 24 unimodular lattices. One of these is the exceptional Leech lattice which has many surprising properties; due to its existence, the answers to many problems such as the kissing number problem and sphere packing are known in 24 dimensions but not in many lower dimensions. The Leech lattice is closely related to the equally nice length-24 binary Golay code and the Steiner system S(5,8,24). One construction of the Leech lattice is possible because of the remarkable fact that 12+22+32+...+242 is a perfect square.

The 24-cell, with 24 octahedral cells and 24 vertices, is a self-dual convex regular 4-polytope; it has no good 3-dimensional analogue.

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In science

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Astronomy

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In music

There are 24 major and minor keys in Western tonal music, not counting enharmonic equivalents. Therefore, for collections of pieces written in each key, the number of pieces in such a collection; e.g., Chopin's 24 Preludes.

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In sports

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In other fields

Image:Prague Apr04 015.jpg

Twenty-four is:

  • The number of hours in a day.
  • Motion picture film is traditionally projected at 24 frames per second.
  • The number of cycles in the Chinese solar year.
  • The number of books in the Tanakh.
  • Usually the number of teeth in a human child's mouth.
  • The number of karats that represents 100% pure gold.
  • The number of bits a computer needs to represent truecolour images (for a maximum of 16,777,216 colours).
  • The number of letters in both the modern and classical Greek alphabet. For the latter reason, also the number of chapters or "books" into which Homer's Odyssey and Iliad came to be divided.
  • The designation of US Interstate 24, a freeway that runs from Tennessee to Illinois.
  • 24, the popular television series. Each season of the show covers 24 hours in the life of fictional CTU agent Jack Bauer.
  • The number of points in backgammon.
  • When pronounced "two-four", a 24-pack of beer (Canadianism).
  • A children's mathematical game involving the use of any of the 4 standard operations on 4 numbers on a card to get 24.
  • "24" is the name of a song by Welsh musician Jem
  • The nursery rhyme Sing a Song of Sixpence has the line "four and twenty blackbirds, baked in a pie".
  • The maximum number of Knight Companions in the Order of the Garter.
  • Historical years: 24 A.D., 24 B.C., or 1924
  • This number is considered as unlucky in Cantonese culture because it is pronounced as "easy to die". For this reason many buildings skip this floor number. The same goes for 34, 44, etc. since 4 is pronounced as "die".
  • In Brazil, the number 24 holds a strong popular association with homosexuality, as there is a popular betting game, the Jogo do Bicho (Animal Game) in which 24 is the "deer" number. The brazilian word for deer, "veado", is also used as a depreciative slang, used against homosexuals.ca:Vint-i-quatre

da:24 (tal) de:Vierundzwanzig es:Veinticuatro eo:Dudek kvar fr:24 (nombre) ko:24 ia:24 it:Ventiquattro he:24 (מספר) lt:24 (skaičius) nl:24 (getal) ja:24 nap:Vintiquàtte no:24 (tall) pl:24 (liczba) pt:Vinte e quatro ru:24 (число) sl:24 (število) fi:24 (luku) sv:24 (tal) zh:24

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