Why I am facing the condition problem in C?

what's is going wrong here.....if I enter 4123456789098 this then by dividing this number with 10^12 then it should be equal to 4 but it is not.......??

JUST IGNORE THE BELOW THING....SORRY FOR THAT!!

jdkjkjdgkdglhdlashghgh oadgjl adfj kjkja kjafj kjapajpjfouqeihqeiy

My code:

#include <stdio.h>
#include <cs50.h>
#include <math.h>

int main(void)
{
    while (true)
    {
        long long int id = get_long("Number: ") ;
        int k = 0 ;
        while (id != 0)
        {
                id = id / 10 ;
                k++ ;
        }
        printf("%i\n", k) ;

        // VISA

        if (k == 13)
        {
            int x = id / pow(10 , 12) ;

            if (x == 4)
            {
                printf("VISA\n") ;
                break ;
            }

            else
            {
                printf("INVALID V\n") ;
            }
        }

        // AMEX

        else if (k == 15)
        {
            int y = id / pow(10 , 13) ;

            if (y == 34 || y == 37)
            {
                printf("AMEX\n") ;
                break ;
            }

            else
            {
                printf("INVALID A\n") ;
            }
        }

        // VISA or MASTERCARD

        else if (k == 16)
        {
            int z_M = id / pow(10 , 14) ;
            int z_V = id / pow(10 , 15) ;

            if (z_M >= 51 && z_V <= 55)
            {
                printf("MASTERCARD\n") ;
                break ;
            }

            else if (z_V == 4)
            {
                printf("VISA\n") ;
                break ;
            }

            else
            {
                printf("INVALID V or A\n") ;
            }

        }

    }
}

Output:

Number: 4123456789098
13
INVALID V

Expected Output:

Number: 4123456789098
13
VISA

Thanx in advance for any suggestions....!!