C variable specified as a long long but recognized as an int

Question

I'm working on a program that checks the validity of credit card numbers for the CS50 class I'm taking (it's legal I swear haha) and I'm currently working on correctly getting the first two numbers of each CC# to check what company it is from. I've commented what each part does for clarity and also commented where my problem arises.

#include <stdio.h>
#include <stdlib.h>
#include <cs50.h>
#include <math.h>
#include <string.h>
int main(void)
{
  long long ccn = get_long_long("Enter CCN: \n");
  int count = 0;
  long long ccn1 = ccn;
  // finds the amount of digits entered and stores that in int count.
  while (ccn1 != 0)
  {
     ccn1 /= 10;
     +count;
  }
  printf("%i \n", count);
  // ln 17- 19 should take int count, subtract two, put that # as the power of 10, 
  // then divide the CC# by that number to get the first two numbers of the CC#.
  long long power = count - 2;
  // here is where i get the error. its a long long so it 
  // should hold up to 19 digits and im only storing 14 max 
  // but it says that 10^14th is too large for type 'int'
  long long divide = pow(10,power);
  long long ft = ccn / divide;
  printf("power: %i \n", power); //ln 20-22 prints the above ints for debug
  printf("Divide: %lli \n", divide);
  printf("First two: %lli \n", ft);
  string CCC;
  // ln 24-35 cross references the amount of digits in the CC#
  // and the first two digits to find the comapany of the credit card
  if ((count == 15) && (ft =  34|37))
  {
    CCC = "American Express";
  }
  else if ((count == 16) && (ft = 51|52|53|54|55))
  {
    CCC = "MasterCard";
  }
  else if ((count = 13|16) && (ft <=49 && ft >= 40))
  {
      CCC = "Visa";
  }
  printf("Company: %s\n", CCC);
}

Answer 1

The first issue is the +count in the loop. This should be ++count . Because of this, count stays at 0 and power = -2 . You can avoid all that power stuff. You already have the loop, you can use it to get the first two digits:

int ft = 0;
while (ccn1 != 0)
{
    // When you are down to 10 <= ccn1 < 100, store it
    if (ccn1 < 100 && ccn1 > 9) ft = ccn1;
    ccn1 /= 10;
    ++count;
}

Your second issue is how you do your comparisons.

if ((count == 15) && (ft =  34|37))

First, = is assignment, and == tests equality. Second, | is bitwise OR, || is logical OR. Third, you can't test multiple values like that. Correct way:

if ((count == 15) && (ft == 34 || ft == 37))