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.^[1] 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.^[2]

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.

References

1. ^ http://eclipse.gsfc.nasa.gov/SEsaros/SEsaros084.html
2. ^ http://eclipse.gsfc.nasa.gov/LEsaros/LEsaros084.html