12

12 is the natural number that follows 11 and precedes 13. In base ten it is written as 12. It is a composite number with prime factorization 2^2 × 3, and its divisors are 1, 2, 3, 4, 6, and 12.

It is the smallest abundant number, since the sum of its proper divisors (1 + 2 + 3 + 4 + 6) is 16, greater than 12. It has six divisors, and is among the early highly composite numbers, meaning it has more divisors than any smaller positive integer.

Twelve is a common grouping in many contexts: a dozen items; twelve months in a year; twelve hours on a clock; the zodiac has twelve signs; and many traditions reference sets of twelve figures, such as the twelve apostles.

In science, 12 is the atomic number of magnesium (Mg). In geometry, a dodecagon has twelve sides, and a regular dodecahedron has twelve pentagonal faces. In numerals, XII is the Roman numeral for 12, and in base-12 arithmetic, the symbol for twelve is written as “10.”