84 (number)
Appearance
| ||||
---|---|---|---|---|
Cardinal | eighty-four | |||
Ordinal | 84th (eighty-fourth) | |||
Factorization | 22 × 3 × 7 | |||
Divisors | 1, 2, 3, 4, 6, 7, 12, 14, 21, 28, 42, 84 | |||
Greek numeral | ΠΔ´ | |||
Roman numeral | LXXXIV | |||
Binary | 10101002 | |||
Ternary | 100103 | |||
Senary | 2206 | |||
Octal | 1248 | |||
Duodecimal | 7012 | |||
Hexadecimal | 5416 |
84 (eighty-four) is the natural number following 83 and preceding 85.
In mathematics
84 is:
- the sum of the first seven triangular numbers (making it a tetrahedral number).[1]
- the sum of a twin prime (41 + 43).
- a semiperfect number, being thrice a perfect number.
- a palindromic number and a repdigit in bases 11 (7711), 13 (6613), 20 (4420), 27 (3327), and 41 (2241).
- 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.[2] 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.[3]
In other fields
Eighty-four is also:
- The year AD 84, 84 BC, or 1984.
- The number of years in the Insular latercus, a cycle used in the past by Celtic peoples,[4] equal to 3 cycles of the Julian Calendar and to 4 Metonic cycles and 1 octaeteris
- 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 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 B-Side to "Up All Night" (Take That song)
- British Army term for the 84mm Carl Gustav recoilless rifle.
- How many years it takes Uranus to orbit the sun once
See also
References
- ^ "Sloane's A000292 : Tetrahedral numbers". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation. Retrieved 2016-05-29.
- ^ http://eclipse.gsfc.nasa.gov/SEsaros/SEsaros084.html
- ^ http://eclipse.gsfc.nasa.gov/LEsaros/LEsaros084.html
- ^ Bede (731). Ecclesiastical History of the English People., 2.2, Latin original. See Easter controversy#Synod of Whitby in 664 and Computus.