2591

This number is a prime.

The only prime less than a googol that is a reverse concatenation of the n first odd squares (n=3). [Loungrides]

2591 is the smallest prime p such that p divides the numerator of the Bernoulli number B(p-17). [Luen]

2591 is the (2+5+9+1)th Honaker prime. [Watson]

π(2591) is the (2+5+9+1)th semiprime containing at least 1 digit 7. Note that 17 = (2+5+9+1). [Worrom]