**Perfect number **is a number which is equal to sum of its
divisor.For eg,divisors of 6 are 1,2 and 3.The sum of these divisors
is 6.So 6 is called as perfect number.

Here input is accepted by variable n.Divisor d is used whose initial value is 1 and variable sum is used whose initial value is 0.The divisor d divides the variable n and then adds itself to variable sum if the remainder is 0.The divisor is then incremented by 1.This process continous until divisor d is less than or equal to n/2.At the end,if the variable sum is equivalent to variable n,then the variable n is perfect number. Else it is not a perfect number.

#include < stdio.h > #include < conio.h > void main() { int n,d,sum; clrscr(); printf("\n Enter n : "); scanf("%d",&n); sum = 0; d = 1; while ( d<= n/2) { if ( n % d == 0 ) { sum = sum + d; } d++; } // while if ( sum == n ) printf("\n %d is perfect",n); else printf("\n %d is not perfect",n); } // main