Let f(n) be the sum of the positive integer divisors of n. If n is prime and f(f(n)) is also prime, then call n a bouncy prime. What is the smallest bouncy prime?
+33616 Let f(n) be the sum of the positive integer divisors of n. If n is prime and f(f(n)) is also prime, then call n a bouncy prime. What is the smallest bouncy prime?
3 is prime. It has positive integer divisors 1 and 3, so f(3) = 4.
4 has divisors 1, 2 and 4, so f(4) = 7 which is prime.
Hence n = 3 is a bouncy prime.
This doesn't hold for n = 2, so n = 3 is the smallest bouncy prime.
