21-SumOfDigitsOfNum.c

#include<stdio.h>
int main(){
	int n,r,sum=0;
	printf("Enter the number: \n");
	scanf("%d",&n);

	while(n != 0){

		r = n % 10;
		sum = sum + r;
		n = n/10;
	}
	printf("%d",sum);
	return 0;
}