The largest 5 digit number having 3 different digit is
9876543
9999876
9876 is the largest four digit number you can make if all the digits must be different.
98642
The largest 3 digit number whose digits are all primes is 777. The largest 3 digit number with different prime digits is 753.
10023?
99987
9998888
9876 (:
999 is the largest 3-digit number.
9797 is the largest two digit prime number.