# Difference between revisions of "Factorial prime"

This article defines a property that can be evaluated for a prime number. In other words, every prime number either satisfies this property or does not satisfy this property.
View other properties of prime numbers | View other properties of natural numbers

## Definition

A factorial prime is a prime that differs from a factorial by . In other words, it is a prime of the form .

## Occurrence

### Initial values

The initial values of factorial primes are given as: 2, 3, 5, 7, 23, 719, 5039, [SHOW MORE] View list on OEIS

The first four primes  are factorial primes. However, factorial primes become much rarer after that. The next two factorial primes are  and .

The initial values of  for which  is prime are . Note that, by Wilson's theorem,  cannot be prime if  is prime, for . This explains, for instance, why  and  are not prime.  are also Brown numbers -- they are solutions to Brocard's problem of  being a perfect square.

The initial values of  for which  is prime are: .