Comparison in c incorrect for integers other than 2?

I am writing a function to determine the prime factors of a number and return them in a doubly linked list. The code is as below.
(create_list, add_to_tail, and print_DLL perform operations on the DLL and work fine).

DLL* primefactors(int a, DLL *factors){
	int i;
	int primes[40] = {
		2,		3,		5,		7,		11,		13,		17,		19,		23,		29,
		31,		37,		41,		43,		37,		53,		59,		61,		67,		71,
		73,		79,		83,		89,		97,		101,	103,	107,	109,	113,
		127,	131,	137,	139,	149,	151,	157,	163,	167,	173};
	
	factors = create_list(1);		// create with node of "1" to begin with
	
	i = 0;
	while(i < 40 && a != 1){
		if (a % primes[0] == 0){
			printf("%d is a factor of %d; ", primes[i], a);
			add_to_tail(factors, primes[0]);
			a = a / primes[0];
			printf("remainder is %d\n", a);
		} else {
			printf("%d is not a factor of %d; increasing to %d\n", primes[i], a, primes[i + 1]);
			i++;
		}
	}
	print_DLL(factors);
	return factors;
}

The function works correctly for testing factors of 2, but does not recognise higher primes as factors.
e.g. primefactors(8) correctly gives 1, 2, 2, 2; but primefactors(24) gives 1, 2, 2, 2 and then doesn't recognise 3 as a factor, instead running to the end of the list of primes (ignore the 1 at the beginning of the list please).

Why is this and how can it be fixed please? I'd thought that a / prime[i] would give an accurate integer as both a and prime[i] are ints, avoiding float comparison issues.

Thank you!

As pointed out by Barmar and Some programmer dude in the comments, the division should be with primes[i] instead of primes[0]. With this correction it works. Thanks!