Five or six. Numerals only. No letters.
How am i supposed to know!
Usually on back of card next to signature box. Three digits.
There are 16 digits on a credit card.
It is the last three digits on the back of your card near (or on) the signature line.
Visa verification Code is different from the card verification code/value which is the last three last digits behind the card (as in 4563 523- 523 is the cvc or cvv). For more secure and advanced practises ther is the introduction of 'chip and pin' which requires the customer to key in a secret code after their card has been run on a pdq(process data quickly) machine. Not all card issuers though have taken into it.
All of the digits you've listed are significant. If we're supposed to perform some operation on them, the least number of significant figures in any number of the problem determines the number of significant figures in the answer.
There are countless versions of Visa/Mastercards. What determines their eligibility is the BIN number (first 6 digits). There is no harm in trying to add it to your account because the worst it could do is not allow it.
It isn't clear what the question is. If you are supposed to multiply or divide, and if by "signification figures" you mean significant digits, do the multiplication (or division), then round to three significant digits - since the least-precise of the numbers only has three significant digits.
12 digits.12 digits.12 digits.12 digits.
6 digits
The purpose of a CVV number on a credit card is the Card Verification Value and is a extra number printed on the debit or credit card. It is used as an anti fraud number and is usually 4 digits and does not appear on any billing statement.
A quadrillion has 16 digits.