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- Why is 1 not a prime number? 14 answers
I was wondering the reason behind defining the Prime Numbers in a manner of which $1$ isn't an example. I read in Rotman's A First Course in Abstract Algebra that one reason that $1$ is not called a prime is that many theorems involving primes would otherwise be more complicated to state.
So, here are my questions,
Can anyone give examples of many theorems involving primes would be complicated to state had $1$ been considered a prime?
What are other reasons for not considering $1$ a prime apart from what Rotman said?