Well, I could write about the rest, modular algebra, inversibility of x in mod n, why we use the product of two primes, how we are lucky to generate prime numbe

Well, I could write about the rest, modular algebra, inversibility of x in mod n, why we use the product of two primes, how we are lucky to generate prime numbers, what is modular exponentiation and why it allows us to encrypt and decrypt messages, and finally, why having a public key allows you to encrypt a message but doesn't allow you to decrypt one : where does the asymetry comes from. That's what I find interesting (not instantly intuitive).