Here is an implementation of while loop in C to find numbers whose sum of cubes of individual numbers is that number. You can go a step further and make it so that you accept value of i and n.

main(){
int i = 1, a, b, c, n = 1000;
printf("\n Enter a number between 1 and 1000>> ");
while(i > 0 && i < n){
a = (i % 10 * i % 10 * i % 10);
b = (i/10 % 10 * i/10 % 10 * i/10 % 10);
c = (i/100 % 10 * i/100 % 10 * i/100 % 10);
if(a + b + c == i){
printf("\nSum of cubes of the individual digits of %d is %d itself [%d = %d + %d + %d]\n", i, i, i,a,b,c);
}
}
}