1. The first digit – This is the Major Industry Identifier (MII), it shows which category the organization that issued the card belongs to:

1,2 – Airlines
3 – Travel & entertainment
4,5 – Banks, financial companies
6 – Merchandising & banking
7 – Fuel companies
8 – Telecommunications
9 – National bank


2. The first 6 digits – Issuer Identification Number (IIN). It indicates the company that issued the card and its type.

Visa: 4xxxxx
Mastercard: 51xxxx – 55xxxx
Discover: 6011xx, 644xxx, 65xxxx
Amex: 34xxxx, 37xxxx

Can be found by IIN. For example, 376211 – Singapore Airlines Gold Card – KrisFlyer Amex system. 529962 – Prepaid Much-Music MasterCard.


3. Digits from 7th to the one before the last – this is the card owner`s identification number (account No.).
There are a trillion possible combinations.

4. The last digit – check digit. It is used to verify the number`s correctness according to the Luhn algorithm.

How to check if your credit card number is correct:

1) Take your card number:

4417 1234 5678 9113

2) Multiply every second digit (from the right side):

(4 x2) 4 (1 x2) 7 (1 x2) 2 (3 x2) 4 (5 x2) 6 (7 x2) 8 (9 x2) 1 (1x2) 3
-------------------------------------------------------------------------------------
(8) 4 (2) 7 (2) 2 (6) 4 (10) 6 (14) 8 (18) 1 (2) 3

3) Add the multiplied digits with those that were not multiplied; if a two-digit number is formed after addition, then add those two digits (e.g., 14= 1 + 4):

8+4+2+7 + 2+2+6+4 + 1+0+6+1+4+8 + 1+8+1+2+3 = 70

If the result is divisible by 10, then the card number is correct!