There is no highest hexadecimal number. Hexadecimal, like decimal and binary, is a positional number system. This means that you can keep adding digits to the left to represent larger and larger numbers.
For example, the largest 8-digit hexadecimal number is FFFFFFFF, which is equivalent to 4,294,967,295 in decimal. However, you can easily represent a larger number by adding another digit, such as 100000000.
In summary, there is no limit to the size of a hexadecimal number.
