9463

This number is a prime.

Define a function f(n) as follows: interpret the decimal digits of n as if they are hexadecimal (base 16) then convert to decimal. For example, f(100) = 256. 9463 is a prime p for which f(p), f(f(p)), f(f(f(p))), and f(f(f(f(p)))) are all primes: 37987, 227719, 2258713, and 36013843. There are only 15 primes of this type less than 10000. [Keith]