1651

Number
$1651$ (one thousand, six hundred and fifty-one) is:
 * $13 \times 127$


 * The $26$th heptagonal number after $1, 7, 18, 34, 55, 81, 112, \ldots, 874, 970, 1071, 1177, 1288, 1404, 1525$:
 * $1651 = \displaystyle \sum_{k \mathop = 1}^{26} \left({5 k - 4}\right) = \dfrac {26 \left({5 \times 26 - 3}\right)} 2$