# 24 (number): Map

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24 (twenty-four) is the natural number following 23 and preceding 25.

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.

## 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

## In other fields

Astronomical clock in Prague
24 is also:
• 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 Carat 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.

## Historical years

24 A.D., 24 B.C., 1924, 2024, etc.

## References

1. Neil Sloane, " A046970 formatted as a simple table" The only times n = a(n) are for n = 1, 24. The table only goes up to 60, though.