30 (number)

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 astronomy

Messier object M30, a magnitude 8.5 globular cluster in the constellation Pegasus
The New General Catalogue object NGC 30, a double star in the constellation Pegasus
The Saros number 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. Further, the Saros number 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

Thirty is:

The atomic number of zinc
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.
The designation of E30, the European route from Cork to Samara.
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.
The number of cars in the Nintendo 64 game F-Zero X.
Historical years: 30 A.D., 30 B.C., or 1930

Categories: Integers