Question

Given, $f\left(x\right)=$ sum of all natural numbers which can divide $x$ completely. Find : $f(6)$

Answer 1

$f\left(6\right)=$ Sum of all natural numbers which can divide $6$ completely,
Therefore, $f\left(6\right)=1+2+3+6=12$

So, $12$ is the natural number which can divide $6$ completely.