What palindromic prime number of n digits reads the same upside down or when viewed in a mirror?
Some examples for n=2 or 3:
11, 101, 181.
How far can you go?
Rem: Only digits 0,l and 8 qualify.
With the exception of 11, all such primes will have odd n because palindromes with an even number of digits are divisible by 11.
Here is a list of the first 22 such numbers
https://oeis.org/A068188
This site gives a very large number (n=180055)
http://mathworld.wolfram.com/TetradicNumber.html

Posted by Jer
on 20120504 11:21:40 