Sum of all proper divisors from 1 to N | C ++ implementation to find sum of all proper divisor of number up to N ; Utility function to find sum of all proper divisor of number up to N ; Loop to iterate over all the numbers from 1 to N ; Find all divisors of i and add them ; Subtracting ' i ' so that the number itself is not included ; Driver Code
#include <bits/stdc++.h> NEW_LINE using namespace std ; int properDivisorSum ( int n ) { int sum = 0 ; for ( int i = 1 ; i <= n ; ++ i ) { for ( int j = 1 ; j * j <= i ; ++ j ) { if ( i % j == 0 ) { if ( i / j == j ) sum += j ; else sum += j + i / j ; } } sum = sum - i ; } return sum ; } int main ( ) { int n = 4 ; cout << properDivisorSum ( n ) << endl ; n = 5 ; cout << properDivisorSum ( n ) << endl ; return 0 ; }