1261

Number
$1261$ (one thousand, two hundred and sixty-one) is:
 * $13 \times 97$


 * The $21$st centered hexagonal number after $1, 7, 19, 37, 61, 91, 127, 169, 217, 271, 331, 397, 469, 547, 631, 721, 817, 919, 1027, 1141$:
 * $1261 = \displaystyle 1 + \sum_{k \mathop = 1}^{21 - 1} 6 k = 21^3 - 20^3$