23
23
The smallest prime number, of course, is 2. The smallest prime number whose digits add up to 2 is, of course, 2. The next-smallest is 11. It is left as an exercise for the reader to determine whether the other numbers whose digits add up to 2 (e.g. 101, 1001, 10001) are prime.
Smallest is 11 & Largest is 77.
I think it will be 17. The sum of digits is 8, which is the cube of 2.
The largest three digit prime number whose digits are all primes is 773.
The largest 3 digit number whose digits are all primes is 777. The largest 3 digit number with different prime digits is 753.
1155
111111
The smallest positive integer is 3.
7777
121