Hi, I stumbled upon a question in my homework that mentioned sigma functions, and as I under stood, a sigma function is the sum of the factors of a number. Ex. f(5)= 5+1 (factors) = 6.

I would like to know why this is so, Sigma function, does it have any other purpose ? And I thought functions are represented by equations? I hope my questions are clear because I feel like they are not >.<!

Thank you in advance!

-Cheers!