Hey! As Codeforces becomes more and more like MathForces, would love to share with you all a handout I wrote to help teach some introductory number theory. There is a handout explaining some basic techniques, followed by five 'dashes' meant to test your understanding. Hope you enjoy!

Prime Factors and Divisors Handout

Prime Factors and Divisors Contest 1
Prime Factors and Divisors Contest 2
Prime Factors and Divisors Contest 3
Prime Factors and Divisors Contest 4
Prime Factors and Divisors Contest 5