7701

Number
$7701$ (seven thousand, seven hundred and one) is:
 * $3 \times 17 \times 151$


 * The $51$st octagonal number, after $1$, $8$, $21$, $40$, $65$, $\ldots$, $5985$, $6256$, $6533$, $6816$, $7105$, $7400$:
 * $7701 = \displaystyle \sum_{k \mathop = 1}^{51} \left({6 k - 5}\right) = 51 \left({3 \times 51 - 2}\right)$