Credit card visa usually starts with 4. Credit card organizations can be distinguished by the first number of the card number. Usually, cards with card number starting with 6 are UnionPay cards, cards with card number starting with 4 are cards with Visa logo, cards with card number starting with 5 are cards with Master logo, and cards with card number starting with 3 are cards with JCB logo.

The card number of a credit card consists of three parts: the issuer's identification code (BIN number), the issuer's custom bit and the check code.