Generally, the signature on the back of a credit card will be printed with seven digits. The first four digits are the last four digits of the card number, and the last three digits are the security verification code (CVV/CVC/CVN). This security verification code is very important, only available on credit cards, and can't be found anywhere else. The security verification code of each card is different, just like the card number and expiration date, which cannot be disclosed, because the security code is mainly used in telephone channels or online channels, or authorized payment by hotels. This is also a credit card.