Factors of a number in C++

Factors are those numbers that are multiplied to get a number.

For example: 5 and 3 are factors of 15 as 5*3=15. Similarly other factors of 15 are 1 and 15 as 15*1=15.

The program to display the factors of a number are given as follows.

Example: 

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

#include <iostream> using namespace std; int main() { int n, i; cout << "Enter a positive integer: "; cin >> n; cout << "Factors of " << n << " are: " << endl; for(i = 1; i <= n; ++i) { if(n % i == 0) cout << i << endl; } return 0; }

Enter a positive integer: 60
Factors of 60 are: 1 2 3 4 5 6 12 15 20 30 60

Another Example

#include<iostream>
using namespace std;
int main() {
   int num = 20, i;
   cout << "The factors of " << num << " are : ";
   for(i=1; i <= num; i++) {
      if (num % i == 0)
         cout << i << " "; 
   }
   return 0;
}

Output

The factors of 20 are : 1 2 4 5 10 20

In the above program, the for loop runs from 1 to num. The number is divided by i and if the remainder is 0, then i is a factor of num and is printed.

for(i=1; i <= num; i++) {
   if (num % i == 0)
      cout << i << " ";
}

The same program given above can be created using a function that calculates all the factors of the number. This is given as follows −

Another Example

#include<iostream>
using namespace std;
void factors(int num) { 
   int i;
   for(i=1; i <= num; i++) {
      if (num % i == 0)
         cout << i << " ";
   }
}
int main() {
   int num = 25;
   cout << "The factors of " << num << " are : ";
   factors(num);
   return 0;
}

Output

The factors of 25 are : 1 5 25

In the above program, the function factors() finds all the factors of “num”. It is called from the main() function with one parameter i.e. “num”.

factors(num);

The for loop in the function factors() runs from 1 to num. The number is divided by i and if the remainder is 0, then i is a factor of “num” and is printed.

for(i=1; i <= num; i++) {
   if (num % i == 0)
      cout << i << " ";
}