The Pittsburgh Post-Gazette’s Patricia Sabatini explains what credit card numbers mean (other than a quick descent into perpetual debt). It’s fascinating in a mundane sort of way:
Start with the first digit. It, and in some cases the second digit, identifies the card network that will carry the transaction. All MasterCards start with a “5,” for example. Visa cards start with a “4.” Discover cards get a “6.”
American Express cards start with “34” or “37,” while the number “7” is reserved for gasoline cards issued by petroleum companies such as Exxon and Mobil.
The next four or five numbers in the series identify which of the some 13,000 financial institutions in the U.S. issued the card, such as Bank of America, JPMorgan Chase or Citibank.
I knew that the first digit indicated the type of card. I picked up that tidbit early in my career, when I was empowered to issue refunds in response to certain types of customer complaints. Purchases made by card had to be refunded by card, so we were trained in filling out refund slips (this was long before electronic transactions).