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

Cardinal	thirty
Ordinal	thirtieth
Numeral system
Factorization
Divisors	2, 3, 5, 6, 10, 15
Roman numeral	XXX
Binary	11110
Hexadecimal	1E
Hebrew	ל (Lamed)

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 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