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 * 0.1;
    }
    return rev_num;
}

prime_t nextPalindrome(prime_t n) {
    n++;
    int digits = 0;
    prime_t num = n;
    do {
        digits++;
    } while((num *= 0.1) > 0);

    prime_t half = digits * 0.5;
    prime_t left = n * pow(0.1, half);
    prime_t r_left = reverseDigits(left);
    if(r_left % 2 == 0) {
        return nextPalindrome(((int)(n * pow(0.1, digits-1)) + 1) * pow(10, digits-1));
        r_left = reverseDigits(left);
    }
    prime_t p10h  = pow(10, half);
    prime_t right = n - (left * p10h);

    if(digits % 10) {
        r_left = reverseDigits(left * 0.1);

        if(r_left > right)
            return (left * p10h) + r_left;
        else {
            ++left;
            return (left * p10h) + reverseDigits(left * 0.1);
        }
    } else {
        if(r_left > right)
            return (left * p10h) + r_left;
        else {
            ++left;
            return (left * p10h) + reverseDigits(left);
        }
    }
}

int isPrime(prime_t n) {
    prime_t i;

    if(n == 2)
        return 1;
    else if (n == 3)
        return 1;
    else if (n * 0.5 == 0)
        return 0;
    else if (n % 3 == 0)
        return 0;

    i = 5;
    prime_t c = 2;
    while(i * i < n) {
        if(n % i == 0)
            return 0;
        i += c;
        c = 6 - c;
    }

    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();

    do {
        t = nextPalindrome(t);
    } while(!isPrime(t));

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