7

This number is a prime.

Just showing those entries submitted by 'Firoozbakht': (Click here to show all)

The smallest prime p such that all five numbers p*10^k+1, k < 6 are primes. [Firoozbakht]

7 is the only number n such that n = π(n)! - prime(n). [Firoozbakht]

All 7 numbers n! + nextprime(n), n < = 7 are primes. [Firoozbakht]

1! + 2! + 3! + 4! + 5! = 6 (mod 7). It is the largest known prime (up to 10^5) with this property. [Firoozbakht]