84 (number)

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

In mathematics

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).

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 other fields

Eighty-four is also:

• The atomic number of polonium
• the model number of AGM-84 Harpoon
• WGS 84
• 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
• a town in Pennsylvania: Eighty Four, named after the Eighty Four Lumber company
• The ISBN Group Identifier for books published in Spain
• The year AD 84, 84 BC, or 1984.