30 (number)

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

← 30 31 32 33 34 35 36 37 38 39 → List of numbers — Integers 0 10 20 30 40 50 60 70 80 90 →
Cardinal	30 thirty
Ordinal	30th thirtieth
Factorization	$2\cdot 3\cdot 5$
Divisors	1, 2, 3, 5, 6, 10, 15, 30
Roman numeral	XXX
Roman numeral (Unicode)	XXX, xxx
Binary	11110
Octal	36
Duodecimal	26
Hexadecimal	1E
Hebrew	ל (Lamed)

Look up thirty in
Wiktionary, the free dictionary.

1 In mathematics
2 In science
- 2.1 Astronomy
3 In other fields
4 Historical years
5 Music

[edit] 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. Adding up some subsets of its divisors (e.g., 5, 10 and 15) gives 30, hence 30 is a semiperfect number.

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

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

E₈ has Coxeter number 30.

[edit] In science

The atomic number of zinc

[edit] 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 October 2, 2069 BC and ended on March 18, 572 BC. 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 June 19, 1803 BC and ended on August 18, 487 BC. The duration of Saros series 30 was 1316.2 years, and it contained 74 lunar eclipses.

[edit] In other fields

Thirty is:

The number of days in the months April, June, September and November (and in unusual circumstances February - see February 30)
The total number of major and minor keys in Western tonal music, including enharmonic equivalents
In years of marriage, the pearl wedding anniversary
The duration of the Thirty Years' War
Used to indicate the end of a wire service story. (Possibly a corruption of German fertig - "finished, ready" - or in journalistic context "end of story")
The code for international direct dial phone calls to Greece
The house number of 30 St Mary Axe (The Gherkin)
The designation of Interstate 30, a freeway that runs from Texas to Arkansas
The designation of U.S. Route 30, a highway that runs from Oregon to New Jersey
Various other routes have been numbered "30"; for example, New York State Route 30 which runs from the Pennsylvania border to the Canadian border
The designation of E30, the European route from Cork to Samara
The number of tracks on The Beatles' eponymous album, usually known as The White Album
The number of cars in the Nintendo 64 game F-Zero X
-30-, a motion picture about work in a Los Angeles newspaper, starring Jack Webb and William Conrad
A stage in young adulthood
Part of the name of:
- Thirty odd foot of grunts, the band fronted by actor Russell Crowe
- The movie title 13 Going on 30, starring Jennifer Garner
- The title of the Food Network show 30 Minute Meals
The uniform number of Maury Wills when he played for the Los Angeles Dodgers.