Divisor Sum of Non-Square Semiprime/Examples/119

From ProofWiki
Jump to navigation Jump to search

Example of Divisor Sum of Non-Square Semiprime

$\map {\sigma_1} {119} = 144$

where $\sigma_1$ denotes the divisor sum function.


Proof

We have that:

$119 = 7 \times 17$


Hence:

\(\ds \map {\sigma_1} {119}\) \(=\) \(\ds \paren {7 + 1} \paren {17 + 1}\) Divisor Sum of Non-Square Semiprime
\(\ds \) \(=\) \(\ds 8 \times 18\)
\(\ds \) \(=\) \(\ds 2^3 \times \paren {2 \times 3^2}\)
\(\ds \) \(=\) \(\ds 2^4 \times 3^2\)
\(\ds \) \(=\) \(\ds \paren {2^2 \times 3}^2\)
\(\ds \) \(=\) \(\ds 12^2\)
\(\ds \) \(=\) \(\ds 144\)

$\blacksquare$