56

Number
$56$ (fifty-six) is:


 * $2^3 \times 7$


 * The $6$th tetrahedral number, after $1, 4, 10, 20, 35$:
 * $56 = 1 + 3 + 6 + 10 + 15 + 21 = \dfrac {6 \left({6 + 1}\right) \left({6 + 2}\right)} 6$


 * The $13$th semiperfect number after $6, 12, 18, 20, 24, 28, 30, 36, 40, 42, 48, 54$:
 * $56 = 1 + 2 + 4 + 7 + 14 + 28$