Divisor Sum of 679

Example of Divisor Sum of Integer

$\map {\sigma_1} {679} = 784$

where $\sigma_1$ denotes the divisor sum function.

We have that:

$679 = 7 \times 97$

Hence:

$\ds \map {\sigma_1} {679}$

$=$

$\ds \paren {7 + 1} \paren {97 + 1}$

$\ds $

$=$

$\ds 8 \times 98$

$\ds $

$=$

$\ds 2^3 \times \paren {2 \times 7^2}$

$\ds $

$=$

$\ds 2^4 \times 7^2$

$\ds $

$=$

$\ds \paren {2^2 \times 7}^2$

$\ds $

$=$

$\ds 784$

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