Answer:
The number is: 775
Explanation:
The prime numbers from 1-9 are: 2,3,5,7
To form the greatest three digit prime number where each of the digits is prime and the sum of all three digits is also prime:
- we have to start the number from 7 as the greatest prime number is 7.
- the next digit has to be also 7 so that the number remains bigger.
- if for the ones digit we take prime number seven than the sum of all the three digits will not be prime ( as 7+7+&=21 which is not a prime number).
so we take the digit 5 and the sum will be 19(7+7+5) which is a prime
number.
Hence the number is 775.