1651

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Number

$1651$ (one thousand, six hundred and fifty-one) is:

$13 \times 127$

The $26$th heptagonal number after $1$, $7$, $18$, $34$, $55$, $81$, $112$, $\ldots$, $874$, $970$, $1071$, $1177$, $1288$, $1404$, $1525$:

$1651 = \ds \sum_{k \mathop = 1}^{26} \paren {5 k - 4} = \dfrac {26 \paren {5 \times 26 - 3} } 2$

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