72 is the natural number following 71 and preceding 73.

Cardinal	seventy-two
Ordinal	72nd (seventy-second)
Factorization
Divisors	2, 3, 4, 6, 8, 9, 12, 18, 24, 36
Roman numeral	LXXII
Binary	1001000
Hexadecimal	48

In mathematics

Seventy-two is the sum of four consecutive primes (13 + 17 + 19 + 23), as well as the sum of six consecutive primes (5 + 7 + 11 + 13 + 17 + 19). 72 is a Harshad number and a pronic number.

In normal space, the exterior angles of an equilateral pentagon measure 72 degrees each.

There are 17 solutions to the equation φ(x) = 72, more than any integer below 72, making it a highly totient number.

In science

• The atomic number of hafnium

In astronomy,

Messier object M72, a magnitude 10.0 globular cluster in the constellation Aquarius

The New General Catalogue object NGC 72 , a magnitude 13.5 barred spiral galaxy in the constellation Andromeda

The Saros number of the solar eclipse series which began on -727 August 16 and ended on 752 January 21. The duration of Saros series 72 was 1478.1 years, and it contained 83 solar eclipses.

The Saros number of the lunar eclipse series which began on -407 June 5 and ended on 891 July 25. The duration of Saros series 72 was 1298.1 years, and it contained 73 lunar eclipses.

In other fields

Seventy-two is also:

• The number of hours in three days.
• The total number of books in the Holy Bible in the Catholic version if the Book of Lamentations is considered part of the Book of Jeremiah.
• In dpi, the standard resolution of an Apple Macintosh screen.
• The number of the French department Sarthe.
• The designation of USA Interstate 72, a freeway that runs from Missouri to Illinois.
• The registry of the U.S. Navy's nuclear aircraft carrier USS Abraham Lincoln (CVN-72), named after U.S. President Abraham Lincoln.
• The designation of the Soviet T-72 tank.
• In the movie The Red Violin, the lot number of the Bussotti red violin at the DuVal auction house.
• The year AD 72, 72 BC, or 1972.