For the year A.D. 30, see 30.
Thirty (30, XXX) is the natural number following twenty-nine and preceeding thirty-one. It is a primorial as well as the sum of the squares of the integers 1, 2, 3 and 4. It is a sphenic number. Its divisors are 1, 2, 3, 5, 6, 10, 15 and 30; its factorisation is
Thirty is also:
- The atomic number of zinc.
- The number of edges on the regular icosahedron and the regular dodecahedron.
- The house number of 30 St Mary Axe (The Gherkin)
- The number of days in the months April, June, September and November.
- The number of moons of the planet Saturn.
- In years of marriage, the pearl wedding anniversary.
- The code for international direct dial phone calls to Greece.
- The designation of Interstate 30, a freeway that runs from Texas to Arkansas.
- Thirty odd foot of grunts, the band fronted by actor Russell Crowe