74

This number is a composite.

The first occurrence of a difference between successive primes of 74 follows 404597. [Lehmer]

22796996699 is the 999799787th prime. Note that the sum of digits of the nth prime equals the sum of digits of n. The number 74 is the largest known digit sum with this property (as of August 2004). [Firoozbakht]

The only double-digit number ab such that (ab)^a-(ba)^b is prime, i.e., 74^7-47^4 = 12151275393343 that is a prime. [Loungrides]