18911...16901 (25-digits)

This number is a prime.

                                                 18911 1869118061 1698116901

The only invertible prime p that is the reverse concatenation of five consecutive 5-digit invertible primes: {18911||18691||18061||16981||16901}. Curiously, p is expressible as the sum of two squares: 1246809970015^2 + 580158245526^2. [Bajpai]