120

Number
$120$ (one hundred and twenty) is:


 * $2^3 \times 3 \times 5$


 * The $15$th triangular number after $1, 3, 6, 10, 15, 21, 28, 36, 45, 55, 66, 78, 91, 105$:
 * $120 = \displaystyle \sum_{k \mathop = 1}^{15} k = \dfrac {15 \times \left({15 + 1}\right)} 2$


 * The $8$th hexagonal number after $1, 6, 15, 28, 45, 66, 91$:
 * $120 = 1 + 5 + 9 + 13 + 17 + 21 + 25 + 29 = 8 \left({2 \times 8 - 1}\right)$


 * The $8$th tetrahedral number, after $1, 4, 10, 20, 35, 56, 84$:
 * $120 = 1 + 3 + 6 + 10 + 15 + 21 + 28 + 36 = \dfrac {8 \left({8 + 1}\right) \left({8 + 2}\right)} 6$


 * The $5$th factorial after $1, 2, 6, 24$:
 * $120 = 5! = 5 \times 4 \times 3 \times 2 \times 1$


 * The $6$th untouchable number after $2, 5, 52, 88, 96$.