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

30 is the sum of the first four squares, which makes it a square pyramidal number.

It is a primorial and is the smallest Giuga number.

30 is the smallest sphenic number, and the smallest of the form Failed to parse (Missing texvc executable; please see math/README to configure.): 2\cdot 3\cdot r

Thirty has but one number^{[citation needed]} for which it is the aliquot sum: the square number 841.

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 all coprimes smaller than itself, except for 1, are prime.

A polygon with thirty sides is called a tricontagon.

The icosahedron and the dodecahedron are Platonic solids with 30 edges. The icosidodecahedron is an Archimedean solid with 30 vertices, and the Tutte–Coxeter graph is a symmetric graph with 30 vertices.

E₈ has Coxeter number 30.

30 is a Harshad number.

Since any group G such that |G| = pⁿm, where p does not divide m, has a subgroup of order pⁿ, and 30 is the only number less than 60 that is not either a prime or of the above form, it is the only candidate for the order of a simple group less than 60 that one needs other methods to reject.

Michael Joseph Jackson (August 29, 1958 – June 25, 2009) was an American recording artist, entertainer, and businessman. Often referred to as the King of Pop, or by his initials MJ, Jackson is recognized as the most successful entertainer of all time by Guinness World Records. His contribution to music, dance, and fashion, along with a much-publicized personal life, made him a global figure in popular culture for over four decades. The seventh child of the Jackson family, he debuted on the professional music scene along with his brothers as a member of The Jackson 5 in 1964, and began his solo career in 1971.

In the early 1980s, Jackson became a dominant figure in popular music. The music videos for his songs, including those of "Beat It", "Billie Jean", and "Thriller", were credited with transforming the medium into an art form and a promotional tool, and the popularity of these videos helped to bring the relatively new television channel MTV to fame. Videos such as "Black or White" and "Scream" made him a staple on MTV in the 1990s. Through stage performances and music videos, Jackson popularized a number of complicated dance techniques, such as the robot and the moonwalk, to which he gave the name. His distinctive musical sound and vocal style influenced numerous hip hop, post-disco, contemporary R&B, pop and rock artists.