the bank number of a bank card, also known as the issuing bank line number or institution identification code (BIN), is an identification code consisting of six digits, which is used to identify the issuing bank. The bank number of a bank card is usually printed on the front of the card. The first digit represents the type of card, such as debit card, credit card and prepaid card, and the last five digits represent the issuing bank. The card bank number can be used to judge whether the card is valid, the type of the card and the issuing bank.