1261
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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:
- $1261^2 = ??^3 + ??^3$