custom library (if any)

[jNU5fSEw]

Can a user defined his own library. Also, is there a function for the divisor function of an integer?

[helios]

What do you mean by "library"? In any case, the answer is yes, but how you do it will depend on what kind of library you're talking about.

"Divisor function of an integer"?

[jNU5fSEw]

the divisor function is the number of possible factors of the integer

[jsmith]

No, not predefined. You have to write it yourself.