Credit cards, such as MasterCard, Visa, and Discover, all have unique, identifying numbers as their first digits, with the exception of American Express, Diner’s Club and Carte Blanche, which share the same first digit: the number 3. MasterCard’s unique first digit is 5, while Visa’s is always 4.

What credit cards start with what numbers?

The first digit in your credit-card number signifies the system: