4485

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Number

$4485$ (four thousand, four hundred and eighty-five) is:

$3 \times 5 \times 13 \times 23$

The $39$th octagonal number, after $1$, $8$, $21$, $40$, $65$, $\ldots$, $3008$, $3201$, $3400$, $3605$, $3816$, $4033$, $4256$:

$4485 = \ds \sum_{k \mathop = 1}^{39} \paren {6 k - 5} = 39 \paren {3 \times 39 - 2}$

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