Almost all palindromes are composite
  We study the distribution of palindromic numbers (with respect to a fixed base $g\ge 2$) over certain congruence classes, and we derive a nontrivial upper bound for the number of prime palindromes $n\le x$ as $x\to\infty$. Our results show that almost all palindromes in a given base are composite. 
William D. Banks, Derrick N. Hart, Mayumi Sakata