The number 5 is the first digit of all account numbers associated with which major credit card?

The number 5 is the first digit of all account numbers associated with which major credit card?

The major credit card associated with account numbers that universally start with the digit 5 is Mastercard. The first digit of any credit card number is formally known as the Major Industry Identifier (MII), and it functions as a critical indicator of the payment network or industry that issued the card. For Mastercard, this MII value is specifically designated as 5, which means that every Primary Account Number (PAN) issued on their network will immediately begin with that digit.

This numerical convention allows merchants and payment processors to instantly identify the card’s network, which is essential for routing the transaction correctly through the appropriate payment channels for authorization. This MII distinction is part of the larger ISO/IEC 7812 numbering standard. For comparison, the Visa network uses 4 as its MII, while American Express uses 3, clearly separating the major card networks based solely on the very first number in the account sequence.

Source:

https://www.youtube.com/watch?v=OSkhKzxYvbE