Card Number is also known as “Primary Account Number (PAN)”. The card number on financial cards are usually 16 or 19 digit long. The first 6 or 8 digits of a payment card number (credit cards, debit cards, etc.) are known as the Issuer Identification Numbers (IIN), previously known as Bank Identification Number (BIN). That is because IINs are used by companies other than Banks too. The IINs identify the institution that issued the card.

• “Visa and MasterCard always have 16 digits whereas American Express has 15 digits.

  Visa and MasterCard do not issue credit cards; instead, they use banks (financial institutions) to issue the cards. The structure of the 16 digit PAN (Primary Account Number) includes: system identifier, issuer/bank identifier, bank number, account number, a check digit. [Example for Visa: SBBBBBAAAAAAAAAC]

  For American Express, they issue their credit cards themselves. The structure of their 15 digit PAN is: system identifier, type, currency, account number, a check digit. [Example for AMEX: SSTCAAAAAAAAAAC]” – Steven Loi on www.quora.com

• “Actually, Amex no longer issues all their cards themselves, but for obvious reasons their contracted banks use the same number format” – John Levine on www.quora.com

• “Although 16 digits is a commonly-used number, it would appear that no external force or regulatory agency is forcing credit card companies to be consistent in the number of internally-assigned digits that they use.

• Here’s a look at some others, for comparison” – Garrico Saito on www.quora.com

ISO/IEC 7812 defines the card numbering system.

The purpose of the numbering system is to uniquely identify a card issuing institution in an international interchange or closed environment.

“American Bankers Association” is the registration authority for the Issuer Identification Numbers (IINs).

An IIN is six digits long. The first digit is major industry identifier (MII – refer Table below), followed by 5 digits. This IIN is followed by 9 or 12 individual account identification number depending upon the length of the PAN. The last number is a single digit checksum. The calculation of check sum is done using Luhn’s algorithm.

In 2015, the industry began work on implementing a change to ISO 7812 to increase the length of the IIN to 8 digits. The 2017 revision of the standard defines the new eight digit IIN and outlines a timeline for conversion of existing six digits IINs to eight digit IINs.

There are two types of IINs:

• International Interchange – All interchange IINs are eight digit numbers and each card issuer is entitled to one IIN (outside of its membership of any card schemes, for example an IIN assigned from Visa). Therefore only one IIN will be assigned to each card issuer. This IIN must be used only to identify the card issuer and is used when information is exchanged between the acquirer and the issuer for clearing and settlement.

• Closed Environment – All closed environment IINs are nine digit numbers and can be used for national use ONLY. Closed environment IINs are used when the issuer acquires its own transactions and its network does not accept, allow, or process any card program other than its own.

Card numbers of Visa begin with “4”, MasterCard with “5”, and Discover with “6”. AMEX cards begin with “37” or “34” because American Express cards are “travel and entertainment” cards, while the remaining all come under financial segment. MasterCard website says that additional range of “2“-series numbers (range 222100-272099) would be used by them.

If you wish to know the issuer of any card, then visit https://binlist.net/ and type in the IIN to get the name of the Debit/Credit card issuer Bank.