Visa Debit Cards — San Mateo County Employees Credit Union - IIN 421010
Debit card numbers that start with the Issuer Identification Number (IIN) 421010 are Visa debit cards issued by San Mateo County Employees Credit Union in United States. Note that this is the only IIN range issued by San Mateo County Employees Credit Union, so all cards issued by this provider will be of the format 4210 10XX XXXX XXXX. For more information, call San Mateo County Employees Credit Union at (650) 363-1725.
Anatomy of a San Mateo County Employees Credit Union Visa 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 4 indicates that this is a Visa 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 421010 indicates that this card was issued by San Mateo County Employees Credit Union 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.