Question

Find all the two digit prime numbers neither of whose digits are prime.

Someone helped me yesterday but I do not understand.

Answer 1

You need a list of all digits which are <i>not</i> prime:
1,4,6,8,9
(Note that 1 is not considered a prime).

From a list of prime number from 1 to 100, find the primes that are made up of one or both of these 5 digits. For example, 11 is a prime number made up of digits (1 and 1) that are not prime.

List of prime numbers less than 100
2 3 5 7 11 13 17 19 23 29 31 37 41 43 47 53 59 61 67 71 73 79 83 89 97

Answer 2

For how many two digit prime numbers is the sum of its digits 8