75

Number
$75$ (seventy-five) is:


 * $3 \times 5^2$


 * The $18$th lucky number:
 * $1, 3, 7, 9, 13, 15, 21, 25, 31, 33, 37, 43, 49, 51, 63, 67, 73, 75, \ldots$