There are 16 numbers on a mastercard credit card
There are 16 digits on a credit card.
The typical card has 16 numbers American Express has 15.
Most cases it is three, and they are the last numbers on the back of your card.
16 digits in a credit card number and 3 for the security code on the back of the card.
Credit card ID numbers have three (Discover, Visa, MasterCard) or four (American Express) digits.