Example
Input
Input upper limit: 100
Output
Perfect numbers between 1 to 100: 6, 28
Perfect number is a positive integer which is equal to the sum of its proper positive divisors.
For example: 6 is the first perfect number
Proper divisors of 6 are 1, 2, 3
Sum of its proper divisors = 1 + 2 + 3 = 6.
Hence 6 is a perfect number.
/**
* C program to print all Perfect numbers between 1 to n
*/
#include <stdio.h>
int main()
{
int i, j, end, sum;
/* Input upper limit to print perfect number */
printf("Enter upper limit: ");
scanf("%d", &end);
printf("All Perfect numbers between 1 to %d:\n", end);
/* Iterate from 1 to end */
for(i=1; i<=end; i++)
{
sum = 0;
/* Check whether the current number i is Perfect number or not */
for(j=1; j<i; j++)
{
if(i % j == 0)
{
sum += j;
}
}
/* If the current number i is Perfect number */
if(sum == i)
{
printf("%d, ", i);
}
}
return 0;
}Program to generate perfect numbers in given range
/**
* C program to print all Perfect numbers between 1 to n
*/
#include <stdio.h>
int main()
{
int i, j, start, end, sum;
/* Input lower and upper limit from user */
printf("Enter lower limit: ");
scanf("%d", &start);
printf("Enter upper limit: ");
scanf("%d", &end);
printf("All Perfect numbers between %d to %d:\n", start, end);
/* Iterate from start to end */
for(i=start; i<=end; i++)
{
sum = 0;
/* Check whether the current number i is Perfect number or not */
for(j=1; j<i; j++)
{
if(i % j == 0)
{
sum += j;
}
}
/* If the current number i is Perfect number */
if(sum == i)
{
printf("%d, ", i);
}
}
return 0;
}
/*
Output :
Enter lower limit: 1
Enter upper limit: 1000
All Perfect numbers between 1 to 1000:
6, 28, 496,
*/