64

64 (sixty-four) is the natural number following 63 and preceding 65.

In mathematics

Sixty-four is the square of 8, the cube of 4, and the sixth power of 2. It is the smallest number with exactly seven divisors. It is the lowest positive power of two that is adjacent to neither a Mersenne prime nor a Fermat prime. 64 is the sum of Euler's totient function for the first fourteen integers. It is also a dodecagonal number and a centered triangular number.

Since it is possible to find sequences of 64 consecutive integers such that each inner member shares a factor with either the first or the last member, 64 is an Erdős–Woods number.

In base 10, no integer added up to its own digits yields 64, hence it is a self number.

64 is a superperfect number - a number such that σ(σ(n))=2n.

In science

• The atomic number of gadolinium, a lanthanide

Astronomy

• Messier object M64, a magnitude 9.0 galaxy in the constellation Coma Berenices, also known as the Black Eye Galaxy.

• The New General Catalogue object NGC 64, a barred spiral galaxy in the constellation Cetus

• The Saros number of the solar eclipse series which began on -832 April 11 and ended on 430 May 8. The duration of Saros series 64 was 1262.1 years, and it contained 71 solar eclipses.

• The Saros number of the lunar eclipse series which began on -801 August 9 and ended on 714 February 4. The duration of Saros series 64 was 1514.5 years, and it contained 85 lunar eclipses.

In other fields

A chessboard has 64 squares

Sixty-four is:

• In some computer programming languages, the size in bits of certain data types
• In chess or draughts, the total number of black (dark) and white (light) squares on the game board
• 64 is the name of the premier Russian chess magazine
• The code for international direct dial calls to New Zealand
• The designation of US Interstate 64, a freeway from Missouri to Virginia
• The designation of U.S. Route 64, a highway from Arizona to North Carolina
• The subject of the Beatles song "When I'm Sixty-Four"
• The registry of the U.S. Navy's aircraft carrier USS Constellation (CV-64)
• The number of Braille characters in the old 6-dot system
• In 8-bit home computers, a common shorthand for the Commodore 64
• In video games, the Nintendo 64 video game console and (historically) the Commodore 64. Since 1996, the number 64 has been an abbreviation or slang for Nintendo 64 (though N64 is more common)
• The maximum number of strokes in any Chinese character
• Number of hexagrams in the I Ching
• Number of sexual positions in the Kama Sutra
• Number of demons in the Dictionnaire Infernal
• Slang term referring to a 1964 Chevrolet Impala, often configured as a lowrider, a popular subject among early-90's gangsta rap and today very popular in Dirty South H-Town rap, eg. by rappers such as Paul Wall, Mike Jones, etc.
• The number of classical arts listed in many Indian scriptures. They include: singing, dancing, painting, poetry, playing cards, making arguments, making flower garlands, etc.
• The number of the French department Pyrénées-Atlantiques
• The amount of crayons in the popular Crayola 64 pack
• Base 64 is used for example with Base64 encoding.
• 64 (dog) is a character in the Donald Duck comics universe.
• Number of codons in the RNA codon table under genetic code.

Historical years

64 A.D., 64 B.C., 1964, 2064, etc.

See also

• The 64,000 Dollar Question