That is number theory. Number theory is at the same time extremely profound and very very blunt. Every prime is double of an integer + 1, except for 2. This fo

That is number theory. Number theory is at the same time extremely profound and very very blunt. Every prime is double of an integer + 1, except for 2. This follows because primes are integers, integers are either 2 times n or 2 times n+1 and numbers representable as 2 times n have 2 as a prime factor, if n > 1. Hence, except for 2. Overall, number theory is one example to me how very, very simple concepts are actually hard - because you're not trained to look for them. The proof is just ... obvious once pointed out. But why would you look for it with such simple manners?