3997

Number
$3997$ (three thousand, nine hundred and ninety-seven) is:


 * $7 \times 571$


 * The $37$th centered hexagonal number after $1, 7, 19, 37, 61, 91, 127, \ldots, 2791, 2977, 3169, 3367, 3571, 3781$:
 * $3997 = \displaystyle 1 + \sum_{k \mathop = 1}^{37 - 1} 6 k = 37^3 - 36^3$