99

Number
$99$ (ninety-nine) is:


 * $3^2 \times 11$


 * The $22$nd lucky number:
 * $1, 3, 7, 9, 13, 15, 21, 25, 31, 33, 37, 43, 49, 51, 63, 67, 73, 75, 79, 87, 93, 99, \ldots$


 * The $5$th Kaprekar number after $1, 9, 45, 55$:
 * $99^2 = 9801 \to 98 + 01 = 99$


 * The $8$th integer after $0, 1, 3, 5, 7, 9, 33$ which is palindromic in both decimal and binary:
 * $99_{10} = 1 \, 100 \, 011_2$


 * The $2$nd of the $3$rd pair of consecutive integers which both have $6$ divisors:
 * $\tau \left({98}\right) = \tau \left({99}\right) = 6$

Also see