MathDB

Two positive integers

a

and

b

are prime-related if

a = pb

b = pa

for some prime

p

. Find all positive integers

n

, such that

n

has at least three divisors, and all the divisors can be arranged without repetition in a circle so that any two adjacent divisors are prime-related.
Note that

1

and

n

are included as divisors.

Problem Statement