Lowest prime palindrome greater than time

#include <stdio.h>
#include <math.h>
#include <time.h>
#include <windows.h>

typedef time_t prime_t;

prime_t reverseDigits(prime_t num)
{
    prime_t rev_num = 0;
    while(num > 0)
    {
        rev_num = rev_num*10 + num%10;
        num = num/10;
    }
    return rev_num;
}

prime_t nextOddPalindrome(prime_t n) {
    do {
        n += 2;
    } while(n != reverseDigits(n));

    return n;
}

int isPrime(prime_t n) {
    int i;

    if(n < 2)
        return 0;
    else if(n == 2)
        return 1;

    for(i = 3; i < sqrt(n) + 1; i+=2)
        if(n % i == 0)
            return 0;

    return 1;
}

int main(int argc, char **argv)
{
    time_t t = time(NULL);
    printf("next prime palindrome of %I64u is ", t);

    unsigned int s = GetTickCount();

    if(t % 2 == 0)
        t--;
    do {
        t = nextOddPalindrome(t);
    } while(!isPrime(t));

    printf("%I64u\n", t);
    printf("elapsed %lu milliseconds", GetTickCount() - s);
    return 0;
}