54621

This number is a composite.

54621 is prime if 10^1, 10^2, 10^3, ..., or 10^9 is added to it. This is the smallest number with this property to form a chain of 9 consecutive primes of form 10^i + n, i = 1, 2,... 9. It is followed by 3726723, 5893321, 6379401, .... [Vrba]