First Number: Industry Identifier Take a look at the first digit on a credit card. This digit will tell you two things: The payment network and the industry associated with the card. If the first digit is a 3, the payment network is American Express. Visas start with 4, Mastercards typically with 2 or 5 and Discovers with 6.  Besides the payment network, the first digit identifies which industry the card is associated with. This digit is the Major Industry Identifier (MII): 1 and 2 belong to cards associated with air travel and financial services. 2-6 are typically used for everyday financial and banking uses. 7 is for the petroleum industry. 8 is for health care and telecommunications. 9 is open for use by the government and is basically the “other” category.