30 (number)
Encyclopedia : 3 : 30 : 30N : 30 (number)
30 (thirty) is the natural number following 29 and preceding 31.
| Cardinal | 30 thirty |
| Ordinal | 30th thirtieth |
| Numeral system | |
| Factorization | [2\cdot 3\cdot 5] |
| 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.
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
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.
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
- 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 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
- The number that New York Rangers goalie Henrik Lundqvist wears in the NHL. Lundqvist wore 35 in Sweden, but since number 35 is retired by the Rangers for former goalie Mike Richter, he chose 30 instead
Historical years
30 A.D., 30 B.C., 1930, 2030, etc.
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