78 (seventy-eight) is the natural number following 77 and followed by 79.

Cardinal	seventy-eight
Ordinal	78th (seventy-eighth)
Factorization
Divisors	2, 3, 6, 13, 26, 39
Roman numeral	LXXVIII
Binary	1001110
Hexadecimal	4E

In mathematics

78 is a triangular number, and its factorization makes it a sphenic number.

Karl A. Dahlke proved in 1989 that 78 heptominos of this shape ( ), at a minimum, are required to fill a rectangle.

In science

• The atomic number of platinum

In astronomy,

Messier object M78, a magnitude 8.0 diffuse nebula in the constellation Orion

The New General Catalogue object NGC 78 , a magnitude 12.8 barred spiral galaxy in the constellation Pisces

The Saros number of the solar eclipse series which began on -463 June 9 and ended on 817 July 18. The duration of Saros series 78 was 1280.1 years, and it contained 72 solar eclipses.

The Saros number of the lunar eclipse series which began on -125 April 10 and ended on 1155 May 18. The duration of Saros series 78 was 1280.1 years, and it contained 72 lunar eclipses.

In other fields

78 is also:

• The designation of Interstate 78, a freeway that runs from Pennsylvania to New York.
• In reference to gramophone records, 78 refers those meant to be spun at 78 revolutions per minute. Compare: LP, 33 and 45.
• A standard Tarot deck containing the 22 cards of the major arcana (including the fool) and the 56 cards of the minor arcana make up 78 cards.
• The total number of gifts in the song The Twelve Days of Christmas (since 78 is the 12th triangular number).
• The year AD 78, 78 BC, or 1978.