ELI5 Prime Numbers - why isn’t 1 a prime number?

What are the two reasons that 1 is not classified as a prime number? How did the definition of prime numbers evolve? What is Euclid’s theorem and how does it relate to prime numbers? Explain the Twin Prime Conjecture. How do prime numbers play a crucial role in encryption methods, especially in securing digital communication? ... we explain like I'm five Thank you to the r/explainlikeimfive community and in particular the following users whose questions and comments formed the basis of this discussion: hypertinks, jamcdonald120, viskerratio, vladdy-the-impaler, frostyfingertips and functor7 To the ELI5 community that has supported us so far, thanks for all your feedback and comments. Join us on Twitter: https://www.twitter.com/eli5ThePodcast/ or send us an e-mail: [email protected]