Almost all credit card companies use a standardized system for tracking and billing their customers’ transactions. Since there are so many financial institutions using this system, to avoid confusion between credit card companies, the numbers on your credit card identify which institution “owns” each transaction.
If you take a close look at your credit cards, you’ll probably wonder what all those numbers stand for. Every digit actually stands for something specific.
The first digit in your credit-card number signifies the system:
3 - travel/entertainment cards (such as American Express and Diners Club)
4 - Visa (such as Visa-Branded cash and debit cards)
5 - MasterCard (brand of debit, credit and cash cards)
6 - Discover Card
For American Express, digits three and four are type and currency, digits five through 11 are the account number, digits 12 through 14 are the card number within the account and digit 15 is a check digit.
For Visa, digits two through six are the bank number, digits seven through 12 or seven through 15 are the account number and digit 13 or 16 is a check digit.
For MasterCard, digits two and three, two through four, two through five or two through six are the bank number (depending on whether digit two is a 1, 2, 3 or other). The digits after the bank number up through digit 15 are the account number, and digit 16 is a check digit.
A check digit is an interesting security item. The process of checking your credit card number is done by multiplying the sum of the odd digits by 3, which is then added to the sum of the even digits which, when added to the check digit, will equal a multiple of 10. That is why technology really wonders me.
Although this information might seem apparently useless, knowing more details about your card can be an important source of power in preventing credit card fraud.
Tags: credit card numbers