### C program to check if a number is a perfect number or not :

In this tutorial, we will learn how to find if a number is perfect or not by using C programming language. A positive number is called a perfect number if the *sum of its proper positive divisors* is equal to the number. For example, *6* is a perfect number. Because :

Its proper divisors from 1 to 5 are 1, 2, and 3. Sum is *1 + 2 + 3 = 6* which is equal to the number itself. So, it is a perfect number.

Let’s take a look at the program :

### C program :

#include int main(){ //1 int no; int sum = 0; int divisor = 1; //2 printf("Enter the number : "); scanf("%d",&no); //3 for(divisor = 1;divisor

### Explanation :

*The commented numbers in the above program denote the step number below :*

1. Create one *integer* variable *no* to store the number, one variable *sum* to store the sum of all perfect divisors and one more variable *divisor* that indicate the current divisor.

2. Ask the user to enter a number. Read it and save it in variable *no*.

3. Run one for-loop. This loop will run from *divisor = 1* to *divisor = no – 1*.

4. Check if the current *divisor* is *perfect-divisor* or not, i.e. if the divisor divides the number, the remainder should be *0*. If it is a *perfect-divisor*, add its value to *sum*.

5. Finally, check if the *sum* is equal to the original number or not. If yes, it is a perfect number, else it is not. Print out the message to the user.

### Sample Output :

Enter the number : 567 567 is not a perfect number Enter the number : 6 6 is a perfect number Enter the number : 8128 8128 is a perfect number Enter the number : 496 496 is a perfect number Enter the number : 28 28 is a perfect number