1261

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


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


 * The $4$th integer after $3$, $228$, $671$ whose square is the sum of $2$ coprime cubes:
 * $1261^2 = ??^3 + ??^3$