49

Number
$49$ (forty-nine) is:


 * $7^2$


 * The $7$th square number after $1, 4, 9, 16, 25, 36$:
 * $49 = 7 \times 7$


 * The $10$th powerful number after $1, 4, 8, 9, 16, 25, 27, 32, 36$


 * The $13$th lucky number:
 * $1, 3, 7, 9, 13, 15, 21, 25, 31, 33, 37, 43, 49, \ldots$