Expert: Josh - 7/11/2007

Question
Hello:

Can a fraction be a prime number? If not, why, and if none are prime numbers, are they considered composite numbers?


I thank you for your reply.  

Answer
Can a fraction be a prime number?
> In general, the answer is no. But I guess you could argue that 10/2 (equivalent to 5) is a prime number. But no one would consider an integer such as 5 as a fraction. It is just unhelpful. Apart from this, prime numbers can never be an irreducible fraction; they must be integers.

"If none are prime numbers, are they (fractions) considered composite numbers?"
> This is a strange way of thinking about fractions. I don't think of them as anything other than fractions. Define what you mean by composite number. I guess we can always write A/B as A*(1/B), would you consider this a composite number?