the card number of a credit card can vary from 13 digits to 19 digits according to international standards, but most of our commonly used credit cards are 16 digits.

digits 1-6 indicate the identification number of the issuing bank. The 7th-12th digits are the serial number of the user card. The 13th digit can distinguish the main card from the secondary card. If it is , it means the main card. If it is 1-9, it means the secondary card. The 14th digit represents the date of issuance of the card statement. The 15th digit represents the card number. If it is lost and needs to be reissued, it will be added with 1 after the card is reissued. The 16th digit is the inspection code.