9221

This number is a prime.

Prime 9221 has an unusual property: if it and the next three primes are used in order as the terms of a continued fraction, as 9221 + 1/(9227 + 1/(9239 + 1/9241)), and then reduced to a single fraction in lowest terms (which in this case is 7264111391848061/787779124441), the numerator and denominator of the resulting fraction are both primes. There are only 12 primes like this less than 10000, with 9221 being the largest one. [Keith]