2551

This number is a prime.

The smallest prime p such that p² + p + 4 is a palindrome. [Russo]

2551 = (2*5*5*1)^0 + (2*5*5*1)^1 + (2*5*5*1)^2. [Rooholamini]

The only prime, less than a googol, that is reverse concatenation of n first powers of 5 (n=3). [Loungrides]

Kosmos-2551 was a Russian reconnaissance satellite that did not make it into orbit. [Estremera]