MasterCard credit card numbers
For MasterCard credit cards, the number is also Sixteen digits long. The very first digit is always a 5 and the 2nd digit is always in between 1-5. The 2nd-3rd, 2nd-4th, 2nd-5th, or 2nd-6th digits correspond to the bank quantity, and the remaining digits up through the 15th are the account quantity. As above, the 16th digit may be the check digit.