33

Number
$33$ (thirty-three) is:


 * $3 \times 11$


 * The $11$th semiprime after $4, 6, 9, 10, 14, 15, 21, 22, 25, 26$:
 * $33 = 3 \times 11$


 * The $10$th lucky number:
 * $1, 3, 7, 9, 13, 15, 21, 25, 31, 33, \ldots$


 * The $1$st of the smallest triple of $3$ consecutive semiprimes:
 * $33, 34, 35$


 * The sum of the first $4$ factorials:
 * $33 = 1 + 2 + 6 + 24 = 1! + 2! + 3! + 4!$

Also see

 * Smallest Sequence of Three Consecutive Semiprimes