7105

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Number

$7105$ (seven thousand, one hundred and five) is:

$5 \times 7^2 \times 29$

The $49$th octagonal number, after $1$, $8$, $21$, $40$, $65$, $\ldots$, $5985$, $6256$, $6533$, $6816$:

$7105 = \ds \sum_{k \mathop = 1}^{49} \paren {6 k - 5} = 49 \paren {3 \times 49 - 2}$

Also see

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