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)
  • the 11th composite number of this form and the third of the form (3², q)
• 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.
• $\frac{99}{70}=1.41428571\dots$ is a commonly used approximation of the irrational number √2
• ".99" is frequently used as a price ender in pricing.

See also

• 99 (disambiguation)