84 (number)

84 (eighty-four) is the natural number following 83 and preceding 85.

← 83 85 → 84
← 80 81 82 83 84 85 86 87 88 89 → List of numbers — Integers 0 10 20 30 40 50 60 70 80 90 →
Cardinal	eighty-four
Ordinal	84th (eighty-fourth)
Numeral system	84
Factorization	$2^2 \cdot 3 \cdot 7$
Divisors	1, 2, 3, 4, 6, 7, 12, 14, 21, 28, 42, 84
Roman numeral	LXXXIV
Binary	10101002
Octal	1248
Duodecimal	7012
Hexadecimal	5416

In mathematics

A hepteract is a seven-dimensional hypercube with 84 penteract 5-faces

Eighty-four is the sum of the first seven triangular numbers (making it a tetrahedral number), as well as the sum of a twin prime (41 + 43). Being thrice a perfect number, 84 is itself a semiperfect number.

Eighty-four is also the lim sup of the largest finite subgroup of the mapping class group of a genus g surface divided by g.

A hepteract is a seven-dimensional hypercube with 84 penteract 5-faces

In astronomy

• Messier object M84, a magnitude 11.0 lenticular galaxy in the constellation Virgo
• The New General Catalogue object NGC 84, a single star in the constellation Andromeda
• The Saros number of the solar eclipse series which began on -181 April 14 and ended on 1099 May 22. The duration of Saros series 84 was 1280.1 years, and it contained 72 solar eclipses. Further, the number of the lunar eclipse series which began on -96 September 13 and ended on 1401 February 28. The duration of Saros series 84 was 1496.5 years, and it contained 84 lunar eclipses.

In sports

Los Angeles Lakers Magic Johnson holds the record for assists in a 6-game NBA Finals Series (1985) with 84

In other fields

dial +84 for Vietnam

Eighty-four is also:

• The year AD 84, 84 BC, or 1984.
• The atomic number of polonium
• The model number of Harpoon missile
• WGS 84 - The latest revision of the World Geodetic System, a fixed global reference frame for the Earth.
• The house number of 84 Avenue Foch
• The number of the French department Vaucluse
• The designation of Interstate 84, two Interstate Highways that run from Oregon to Utah and from Pennsylvania to Massachusetts.
• The code for international direct dial phone calls to Vietnam
• The town of Eighty Four, Pennsylvania
• The company 84 Lumber
• The ISBN Group Identifier for books published in Spain
• A variation of the game 42 played with two sets of dominoes.
• The film "84 Charing Cross Road" (1987) starring Anne Bancroft and Anthony Hopkins
• KKNX Radio 84 in Eugene, Oregon
• The John Larroquette Show ran on NBC from 1993 to 1996 for 84 episodes
• The B-Side to "Up All Night" (Take That song)
• British Army term for the 84mm Carl Gustav recoilless rifle.