CRACKING THE CREDIT CARD CODE has done a great job of cracking the credit card code.

It turns out the first digit identifies the type of card issuer– airline, bank, etc. The first six digits tell you whether it’s Visa, Mastercard, and so on. The seventh and following digits are your account number.  A simple calculation can decide whether the card number is valid. The answer to the equation must be divisible by ten. Try and follow the graphic below.

"Cracking the Credit Card Code" from

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