Number theory is the study of natural numbers and one of the oldest branches of mathematics. Elementary number theory concepts are integrated into K-12 learning experience. This paper will identify ideas and methods in elementary number theory that could be connected to K-12 education and taught in high school classrooms. In fact, Common Core Standards in Mathematics include some basic concepts and skills in elementary number theory. In this study, we will focus on the greatest common divisor, Euclid\u27s algorithm, least common multiple, factorization and divisibility criteria (divisible by 2, 3, 4, 5, 6, 8, 9, and 11). We hope that learning these contents could foster studentsβ interests in mathematics and help them develop computational and reasoning skills
