84 (number) - Definition and Overview

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 science

• The atomic number of polonium

In astronomy,

Messier object M84, a magnitude 11.0 lenticular galaxy in the constellation Virgo

The New General Catalogue object (http://www.ngcic.org/) NGC 84, a single star in the constellation Andromeda

The Saros number (http://sunearth.gsfc.nasa.gov/eclipse/SEsaros/SEsaros1-175.html) 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.

The Saros number (http://sunearth.gsfc.nasa.gov/eclipse/LEsaros/LEsaros1-175.html) 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 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, a freeway that runs 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
• The ISBN Group Identifier for books published in Spain
• The year AD 83, 83 BC, or 1983.