Sigma function - big numbers

[Paroxyzm]

Hi!

I'm new to GMP....

I cannot find any documentation relating to sigma function.


The sigma function is a  sum of all devisors of number n.

Example:
    sigma(2)= 1+2 =3
    sigma(3)= 1+3 =4
    sigma(4)= 1+2+4 =7 
    sigma(6)= 1+2+3 =7
etc...

Can anyone tell me where can I find it??

I'm using C, and C++.



Thanks a lot!
paroxyzm