Folks at $dayJob keep a list of prefixes of credit card numbers that don't satisfy Luhn, currently there's 8 of them. And while we're at it, length of credit c

Folks at $dayJob keep a list of prefixes of credit card numbers that don't satisfy Luhn, currently there's 8 of them. And while we're at it, length of credit card numbers is not fixed, can go from 12 to 19 numbers (both Luhn and non-Luhn).