Mastercard Debit Cards — The Citizens - IIN 551820
Debit card numbers that start with the Issuer Identification Number (IIN) 551820 are Mastercard debit cards issued by The Citizens in United States. The Citizens issues cards under a total of two IIN numbers including this one, so some card numbers issued by The Citizens may start with IIN numbers from one of these other ranges. You can view a list of all two of The Citizens' IIN numbers here. For more information, call The Citizens at (800) 264-5578.
Anatomy of a The Citizens Mastercard Credit Card Number
While credit card number may seem like a random string of digits, they actually contain a large amount of valuable data about the card that can be used for validation and verification purposes.Digit 1 — The MII
The first digit of the card is known as the MII digit, and indicates the credit card's scheme. In this case, the MII of 5 indicates that this is a Mastercard card.Digits 1-6 — The IIN / BIN
The first six digits of the card number, inclusive of the MII, are called the IIN (Issuer Identification Number) or BIN (Bank Identification Number). This sequence uniquely identifies the bank that issued the card. In this case, the IIN of 551820 indicates that this card was issued by The Citizens in United States.Digits 7-15 — The Account Number
Digits 7-15 of the credit card number contain the Primary Account Number, or PAN, issued by the bank to uniquely identify the account holder. These 8 digits are the most important part of the credit card number.Digit 16 — The Check Digit
The last digit of the card number (the 16th digit in most cases) is the check digit, which is calculated by applying a mathematical formula called the Luhn algorithm to the preceding portions of the account number. While not actually part of the account number itself, the check digit is essential to allow easy validation of card numbers and detection of typos, missed digits, etc.