How many two digit prime numbers are there in which both digits are also prime numbers? (For example, 23 is one of these, but 31 is not because 1 is not a prime number)
Need answer AND explination as soon as possible please!!!! Thank you!!!!!
There are 4 of them:
23 37 53 73
The others have either a 1 or a 9 or an even number (>2) in them.
+56 
