1571

This number is a prime.

1571 is the only known prime of form (p!/p# + 1)/p. [Luhn]

1571 = prime(π(1!!*5!!*7!!*1!!)). It is the only known multidigit number with this property. [Firoozbakht]

The smallest prime whose square (2468041) contains all of the even digits. [Gaydos]