You can reverse a number without converting tit to a string: if you take the log base 10 of a number, the integer part is the number of digits in the number minus one: C library function - log10()
] This gives you a for loop :
int digits = (int) log10(num) + 1;
for (int i = 0; i < digits; i++)
Inside the loop, you can extract the least significant digit using the modulus operator, and prepare the number for the next time round the loop by dividing it by ten.
Give it a try, it's quick, efficient, and easy to code!