CreditCard-validation

A credit card number must have between 13 and 16 digits, and this can be checked by using Luhn algorithm. Steps involved in the Luhn algorithm Step 1 – Starting from the rightmost digit, double the value of every second digit,
Step 2 – If doubling of a number results in a two digit number then add the digits of the product to get a single digit number.
Step 3 – Now take the sum of all the digits.
Step 4 – If the total modulo 10 is equal to 0 (if the total ends in zero) then the number is valid according to the Luhn formula; else it is not valid.