5051

This number is a prime.

The last of eight consecutive primes of the form k! + nextprime(k), for k = 0 through 7. [Merickel]

50^50 + 51^51 ends with 5051. It is the only known prime with this property. [Loungrides]

The smallest prime formed from the concatenation in order of two successive composite double-digit numbers. [Loungrides]