5399

This number is a prime.

5399 starts a sequence of five consecutive primes, i.e., 5399, 5407, 5413, 5417, 5419, such that the differences between the successive terms are respectively, 8, 6, 4, 2, that are successive terms of an arithmetic progression. [Loungrides]

5399 is the smallest 4-digit prime number of the form 8k-1, such that 4k-1, 16k-1, and 32k-1 are also primes. [Pace]