Validator and Generator
Use this page to validate a number that contains a Luhn check digit, such as a credit card number using this Luhn check validator. You can also create a new Luhn number by selecting Luhn Generator
Some important numbers, such as IMEI's, identification numbers (for some countries) and credit card numbers include a "check" digit at the end of the number that is used to ensure the number was captured correctly.
More information can be found on the Wikipedia page, Luhn Algorithm