99
99 is the largest two digit number. If I can use the digits anyway I want, then 9 to the 9th power is larger
The largest single digit in our numerical system is 9. Once you write 10, you have two digits.
99
73 is the largest two-digit number that is prime and has prime numbers for both of its digits.
99
97
97
987654
97
It is 97.
97
9987654321