99

99 = 3² x 11.

99 is the largest number that is equal to the sum of its digits plus the product of its digits: 9 + 9 + 9 * 9.

99 is a Kaprekar number. Consider an n-digit number k. Square it and add the right n digits to the left n or n – 1 digits. If the resultant sum is k, then k is called a Kaprekar number.

99² = 9801
98 + 01 = 99

The first few Kaprekar numbers are 1, 9, 45, 55, 99, 297, 703, . . .

99 is 1100011 in base 2 (binary).

99 is the maximum jersey number a player can wear in the National Football League.

Agent 99 was a character played by Barbara Feldon on the 1965-70 television show Get Smart and by Anne Hathaway in the 2008 movie version.

Sources: Number Gossip; Wolfram MathWorld