8

This number is a composite.

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

(8^8+88888)/8 is prime. Note that eight 8s are used. [Firoozbakht]

(π(0)! + π(1)! + ... + π(k)!) is prime only for k = 1,2,..,8 (composite for k>8). [Firoozbakht]

For n > 8, prime(n) > π(n) + sigma(n), so 8 is the only number n such that prime(n) = π(n) + sigma(n). [Firoozbakht]

prime(8) = sigma(8) + phi(8). It is the largest number with this property. [Firoozbakht]