Credit card number usually consists of 13 to 19 digits. The most commonly used length is 16 digits in the card number. The first digit in the number is the Major Industry Identifier, which determines whether the card belongs to one of the payment systems.
For example, 3 is reserved for American Express and Diners Club, 4 for VISA, 5 and 6 for MasterCard and China Union Pay. Currently, it is not possible to clearly determine its membership in the payment system by the first digit of the card. In addition, co-branded cards have become widespread, the processing of which, depending on the conditions, is possible in two payment systems. Therefore, it is necessary to emphasize that the division of cards by the first digit is very conditional. The first few digits of the card number, including the first digit, form the BIN (Bank Identification Number), which is used to uniquely identify the bank that issued the card. Using BIN, payment systems route transactions between the acquirer and the issuer. BIN does not necessarily consist of 6 digits, as is commonly assumed. In modern conditions, this is rather a range of several digits. The last digit in the card number is the verification value calculated using the Luhn algorithm.
Useful link: https://www.bindb.com/bin.php
