Divisability and simple numbers

The eighth book of the series "School Mathematical Mugs" is devoted to the basic concepts and facts that are associated with the divisibility of integers: signs of divisibility, simple and compound numbers, the Euclid algorithm, the main theorem of arithmetic, etc. It is intended for classes with schoolchildren of grades 7-9 . The book includes the development of eight classes of a mathematical circle with detailed theoretical material, examples of tasks of various levels of difficulty, tasks for independent solution and methodological instructions for the teacher. Detailed decisions are given to all the tasks of each lesson. In addition, two not solved problems from this section of mathematics are formulated in the applications, as well as examples of research tasks.
The book is addressed to school teachers of mathematics and leaders of mathematical circles. We hope that she will be interesting to schoolchildren and their parents, students of pedagogical universities, as well as all lovers of elementary mathematics.
5th edition, corrected