30 (number) - Definition

30 (thirty) is the natural number following 29 and preceding 31.

In mathematics

It is a primorial as well as the sum of the squares of the integers 1, 2, 3 and 4. It is the first sphenic number and the first Giuga number. It is the sum of the first four squares, which makes it a square pyramidal number.

30 is the largest number such that coprimes smaller than itself are also prime. It is a Harshad number.

The Chinese word numeral for thirty is 三十.

A polygon with thirty sides is called a tricontagon. Both an icosahedron and a dodecahedron have 30 edges.

In science

• The atomic number of zinc

In astronomy,

Messier object M30, a magnitude 8.5 globular cluster in the constellation Pegasus

The New General Catalogue object (http://www.ngcic.org/) NGC 30, a double star in the constellation Pegasus

The Saros number (http://sunearth.gsfc.nasa.gov/eclipse/SEsaros/SEsaros1-175.html) of the solar eclipse series which began on -2069 October 2 and ended on -572 March 18. The duration of Saros series 30 was 1496.5 years, and it contained 84 solar eclipses.

The Saros number (http://sunearth.gsfc.nasa.gov/eclipse/LEsaros/LEsaros1-175.html) of the lunar eclipse series which began on -1803 June 19 and ended on -487 August 18. The duration of Saros series 30 was 1316.2 years, and it contained 74 lunar eclipses.

In other fields

30 is:

• The house number of 30 St Mary Axe (The Gherkin)
• The number of days in the months April, June, September and November.
• In years of marriage, the pearl wedding anniversary.
• The code for international direct dial phone calls to Greece.
• The duration of the Thirty Years' War.
• The designation of Interstate 30, a freeway that runs from Texas to Arkansas.
• Used to indicate the end of a wire service story.
• The number of tracks on The Beatles' eponymous album, usually known as The White Album.
• Part of the name of:
  • Thirty odd foot of grunts, the band fronted by actor Russell Crowe
• In the title of the movie 13 Going on 30, starring Jennifer Garner.
• In the title of the Food Network show 30 Minute Meals.
• Historical years: 30 A.D., 30 B.C., or 1930
• The number of cars in the Nintendo 64 game F-Zero X.