103

This number is a prime.

P = 103 is the largest emirp P known of the form 10^n + 3 such that the sum of the prime factors, without repetitions, of P (plus its reversal) is equal to P, i.e., for n = 2, 10^2 + 3 = 103 an emipr P = 103; 103 + 301 = 404; 404 = 2^2*101; 2 + 101 = 103. Something analogous occurs also for n = 1. Found by Emmanuel Vantieghem for Puzzle 1255. [Rivera]