Number theory, alongside geometry, is perhaps the oldest area of mathematics and has lost none of its charm over time – quite the opposite: the fascination with timeless problems such as Fermat's conjecture and current applications in cryptography make it seem more vibrant than ever. This book aims to incorporate number theory into the Bachelor curriculum. It is not a comprehensive textbook but intends to convey the material of a one-semester 4+2-hour lecture over 14 weeks, which has been successfully conducted multiple times at FU Berlin. The text spans approximately 140 pages, with 10 exercises each week that are directly integrated into the content. As an additional learning aid, there are hints for many exercises and complete solutions for all exercises at the end of the book, along with a detailed bibliography organized by chapters and accompanied by comments.