C++ Program getting sum of digits of a given number

#include<iostream>
#include<cmath> //for abs function
using namespace std;

int sum_of_digits(int); //function prototype

int main()
{
int num,sum; //defining variables
cout << "Enter any number: ";
cin >> num; //getting number from user
sum=sum_of_digits(num); //calling function
sum = abs(sum); //getting absolute value of sum
cout << "Sum of digits of number " //producing output
<< num
<< " is: "
<< sum
<< endl;

return 0;
}

int sum_of_digits(int number) //function definition
{
int sum=0;
while( number!=0 )
{
sum+=number%10; //getting sum of digits
number/=10;
}
return sum; //returning sum of digits
}