There are 43 3-digit prime numbers which, when reversed, also yield a prime number. (Eight of these are actually consecutive primes).

Of the 43, 15 are simply palindromes (e.g. 929), but of the remaining 14 pairs of numbers (called 'emirp's), one pair in particular exhibits two unique characteristics, one of which is rather surprising.

What are the numbers, and what are their unique characteristics?

(In reply to Up this to D3? by rod hines)

There are not too many operators left which would seem to work with primes to reveal something which I would consider to divulge something other than Add, Subt, and Mult;  rule out Div because of prime.

There is one operation not tested, squaring.

311² = 96721 and  113² = 12769; the digits forming the squares are unique within the number and are in reverse order to each other.

Posted by brianjn on 2009-01-29 23:37:15