Some sample credit card numbers are 4111-1111-1111-1111 for Visa, 3111-1111-1111-1117 for American Express, 5111-1111-1111-1118 for MasterCard, and 6111-1111-1111-1116 for Discover, states Microsoft. Additional sample credit card numbers are available to view and download at Auricsystems.com.
Most credit card numbering systems use the ANSI standard X4.13-1983 standard, although department stores, phone companies and gas companies rely on their own numbering systems, explains HowStuffWorks.
The first digit on a credit card number identifies the specific system, notes HowStuffWorks. For travel and entertainment cards such as Diners Club and American Express, this digit is three. The number is four on Visa cards, five on MasterCard cards and six on Discover cards. The purpose and arrangement of the succeeding digits also varies by system. For instance, digits two through six on Visa cards indicate the bank number, while digits three and four on American Express cards identify type and currency.
The last digit on the sequence is known as the check digit, informs Gizmodo. Issuers generate this number by running the preceding digits through a specialized formula dubbed Luhn's algorithm. The formula is named after its inventor, Hans Peter Luhn. Payment processors use the digit to detect common input errors, such as swapped or missing numbers. Check digits also provide a modicum of protection from unsophisticated hacking and fraud.