16 (sixteen) is the natural number following 15 and preceding 17. 16 is a composite number, and a square number, being 42 = 4 × 4. It is the smallest number with exactly five divisors, its proper divisors being 1, 2, 4 and 8.

Natural Numbers 0-20

In mathematics, natural numbers are those used for counting and ordering.

Some authors begin the natural numbers with 0, corresponding to the non-negative integers 0, 1, 2, 3, and others start with 1, corresponding to the positive integers 1, 2, 3, etc...

Properties of the natural numbers, such as divisibility and the distribution of prime numbers, are studied in number theory. Problems concerning counting and ordering, such as partitioning and enumerations, are studied in combinatorics.