Problem
1. Find the positive divisors of the following integers.
(a) 72
(b) 31
(c) 123
2. Prove that if h|m and m|n, then h|n.
3. Show that two integers divide each other if and only if they are equal
4. Let p and q be two prime numbers. If p = q + 2, then p and q are called "twin prime numbers." Find two pairs of twin prime numbers.