## Abbie23 3 years ago Why isn't 1 a prime number? :)

1. alexwee123

because there is only one factor for 1 and a prime number requires 2

2. mahmit2012

caz many theorem will fail

3. jim_thompson5910

The fundamental theorem of arithmetic states that you can represent any number uniquely as a product of primes If 1 were prime, then a number like 12 can be written as 12 = 2*2*3 12 = 1*2*2*3 12 = 1*1*2*2*3 ...etc so 12 is being represented as a product of primes but it's not unique. So make the representation unique, we exclude 1 from being prime Note: the order of the factors doesn't matter

4. ZSpence

Beacause its too COOL

5. superhelper

because nothing can go into it besides itself

6. SmoothMath

Every prime number has exactly two factors! For example, 2 is prime because it only has factors 1 and 2. 3 only has factors 1 and 3. 5 only has factors 1 and 5. Now, most non-primes, it's easy to realize, "Oh, okay, it has more than 2 factors." 1 is the unique case where it has fewer than 2 factors. Just 1 =/

7. ZSpence

THank you (: