72

Number
$72$ (seventy-two) is:


 * $2^3 \times 3^2$


 * The $16$th semiperfect number after $6, 12, 18, 20, 24, 28, 30, 36, 40, 42, 48, 54, 56, 60, 66$:
 * $72 = 12 + 24 + 36$