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 $17$th semiprime after $4, 6, 9, 10, 14, 15, 21, 22, 25, 26, 33, 34, 35, 38, 39, 46$:
 * $49 = 7 \times 7$


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


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


 * The $11$th happy number after $1, 7, 10, 13, 19, 23, 28, 31, 32, 44$:
 * $49 \to 4^2 + 9^2 = 16 + 81 = 97 \to 9^2 + 7^2 = 81 + 49 = 130 \to 1^2 + 3^2 + 0^2 = 1 + 9 + 0 = 10 \to 1^2 + 0^2 = 1$