In mathematics
- 24 is the factorial of 4 and a composite number, being the first number of the form 23q, where q is an odd prime.
- It is the smallest number with exactly eight divisors: 1, 2, 3, 4, 6, 8, 12, and 24. It is a highly composite number, having more divisors than any smaller number. Adding up all the proper divisors of 24 except 4 and 8 gives 24, hence 24 is a semiperfect number.
- Subtracting one from any of its divisors (except 1 and 2, but including itself) yields a prime number. 24 is the largest number with this property, for to have this property a number cannot be divisible by a prime greater than three, nor can it be divisible by 9 or 16.
- The number of bits a computer needs to represent truecolour images (for a maximum of 16,777,216 colours). (But greater numbers of bits provide more accurate colors. "Truecolor" is one of many possible color representations.)
- The number of a broadcast television channel
- The number of cans or bottles in a beverage case.
- The number of Carats representing 100% pure gold.
- The number of cycles in the Chinese solar year.
- The number of frames per second at which motion picture film is usually projected.
- The number of hours in a day.
- 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.
- 24, television series starring Kiefer Sutherland. Each 24-episode season of the show covers 24 hours.
- The number of points on a backgammon board.
- 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 (see Math 24)
- "24", a song by Welsh musician Jem
- The maximum number of Knight Companions in the Order of the Garter
- The Twenty-fourth Amendment to the United States Constitution is one of the Civil Rights-era amendments, abolishing poll tax requirements in federal elections.
- The designation of US Interstate 24, a freeway that runs from Tennessee to Illinois. Also many other roads called Route 24
- 24 is considered an unlucky number in Cantonese culture because its pronounication is similar to that of "easy to die". For this reason, many buildings skip this floor number. The same goes for 13, 34, 44, etc.
- 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 term for homosexual, although the latter is sometimes spelled with an 'i' as opposed to an 'e'
- #24 is a recurring character on The Venture Bros.
