455

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Number

$455$ (four hundred and fifty-five) is:

$5 \times 7 \times 13$


The $13$th tetrahedral number, after $1$, $4$, $10$, $20$, $35$, $56$, $84$, $120$, $165$, $220$, $286$, $364$:
$455 = \ds \sum_{k \mathop = 1}^{13} \frac {k \paren {k + 1} } 2 = \dfrac {13 \paren {13 + 1} \paren {13 + 2} } 6$


Also see