It is not unreasonable to construct prime numbers to include 1. It is just that, over time, the mathametics community came to the consensus that the set of primes that does not include 1 is more useful.
If primes were constructed to include 1, math would not be seriously different, we would simply have to say 'prime greater than 1' when we want to exlude one. The same way that we often have to say x/=0 when we divide by x.
If primes were constructed to include 1, math would not be seriously different, we would simply have to say 'prime greater than 1' when we want to exlude one. The same way that we often have to say x/=0 when we divide by x.