630

Number
$630$ (six hundred and thirty) is:


 * $2 \times 3^2 \times 5 \times 7$


 * The $18$th hexagonal number after $1, 6, 15, 28, 45, 66, 91, 120, 153, 190, 231, 276, 325, 378, 435, 496, 561$:
 * $630 = \displaystyle \sum_{k \mathop = 1}^{18} \left({4 k - 3}\right) = 18 \left({2 \times 18 - 1}\right)$