"Sixteen" redirects here. For other uses, see Sixteen 16 (sixteen) is the natural number following 15 and preceding 17.Sixteen is a composite number, and a square number, being 42 = 4 × 4. It is the tiniest number with exactly five divisors, its proper divisors being , , and . As a power of 2 it has an aliquot sum one less than itself; 15, and is the fifth composite member of the 3-aliquot tree having the 7 member aliquot sequence (16,15,9,4,3,1,0).It is the fourth power of two. F