There are two types of numbers. Solitary and Friendly/Amicable numbers.
The Solitary numbers don't have friends. Ok, it isn't exactly like that but it's similar.
To define a solitary number, we must first know what a friendly number is. A friendly number, also known as an amicable number, is a number in a friendly pair. The pair of numbers are so related that the sum of one of the number's proper divisors is the other number.
A Solitary number is not in a pair like that. There are many numbers that are thought to be solitary but proving it is hard.
It is hard to find a friendly pair. In fact, most numbers are solitary, including all primes and prime powers.
One of the famous unanswered questions is, is 10 a solitary number?
Well, if you can find a pair for ten, please comment and tell us.
next time: the math of rock paper scissors
