A MasterCard has a total of 16 digits. MasterCard, as well as most major credit card systems, use the ANSI Standard X4.13-1983 system, in which each digit identifies a particular attribute of the card. .
The first digit on any credit card designates the particular system by which it was issued. For example, the MasterCard system is identified by the number 5, American Express and Diners Club credit card numbers start with the number 3, while Visa and Discover Card systems are identified by the numbers 4 and 6, respectively.
Each credit card number has a structure that varies by system. In the MasterCard system, digits two through six are used to identify the bank number, digits seven through 15 designate the account number and digit 16 represents a check digit.