Let 
, so that 
is the digits in the tens place and 
is the digit in the ones place. (Clearly 
.)
There are five possible two digits integers that satisfy this relation:
But the first, third, and fifth candidates are even, so they are not prime. The remaining are prime, however, so
or 
.
There are five possible two digits integers that satisfy this relation:
But the first, third, and fifth candidates are even, so they are not prime. The remaining are prime, however, so