The number of digits in a number system is equal to the base of the system. The decimal system is base 10 and has ten digits. Binary has two bits, which is short for binary digits. Hexadecimal has sixteen digits (0, 1, 2, 3, 4, 5, 6, 7, 8, 9, A, B, C, D, E & F), and so on.
There can be infinitely many of them.
6 digits
6
12 digits.12 digits.12 digits.12 digits.
A quadrillion has 16 digits.
Seven digits.
3 digits!
6 digits
4
11 digits
8 digits.
Five digits.
9 digits