111111. Since there are six digits, there must be a repeated digit, so why not repeat all ones to get the smallest one.
111111 Any 6 digit number less than that would require a 0, which is an even number.
Smallest is 11 & Largest is 77.
The largest 3 digit number whose digits are all primes is 777. The largest 3 digit number with different prime digits is 753.
The largest three digit prime number whose digits are all primes is 773.
Find a four digit number whose digits will be reversed when multiplied by nine?