The last digit of a credit card number is a checksum, so it can catch most of those errors. See https://en.wikipedia.org/wiki/Luhn_algorithm https://en.wikiped

The last digit of a credit card number is a checksum, so it can catch most of those errors. See https://en.wikipedia.org/wiki/Luhn_algorithm https://en.wikipedia.org/wiki/Luhn_algorithm for details