99 (number)

99 (ninety-nine) is the natural number following 98 and preceding 100.

In mathematics

99 is:

a composite number; a square-prime, of the form (p2, q). It is the 11th composite number of this form and the third of the form (32, q). It has an aliquot sum of 57, within an aliquot sequence of two composite numbers (99,57,23,1,0), to the Prime in the 23-aliquot tree.
a Kaprekar number
a lucky number
a palindromic number in base ten
the ninth repdigit
the sum of the cubes of three consecutive integers: 99 = 23 + 33 + 43.
the sum of the sums of the divisors of the first 11 positive integers.