Welcome to the fascinating world of elementary number theory, a branch of mathematics that deals with the properties and relationships of numbers, especially the integers. This book is designed to introduce readers to the beauty and utility of number theory through a collection of problems and their solutions.

Whether you are a student, educator, or enthusiast, this book aims to enhance your understanding of number theory in an engaging and accessible manner. Number theory is often considered the queen of mathematics due to its ancient origins and pure nature.

It is a field that has captivated mathematicians for centuries, from the early discoveries of Euclid and Diophantus to the groundbreaking work of Fermat, Euler, Gauss, and beyond. The allure of number theory lies not only in its rich history but also in its applicability to modern-day cryptography, computer science, and problem-solving.

This book is structured to cater to a wide audience, from beginners to those with some background in number theory. The problems presented range from simple exercises that reinforce basic concepts to more challenging questions that stimulate deeper thinking and exploration.

Each problem is carefully selected and crafted to illustrate a particular aspect of number theory, with solutions provided to guide the reader through the thought process and techniques involved. The journey through this book begins with the fundamentals of divisibility, primes, and the Euclidean algorithm, gradually progressing to more complex topics such as congruences, and Diophantine equations.

Along the way, readers will encounter famous theorems and conjectures that have shaped the field, including the Fundamental Theorem of Arithmetic, Fermat's Little Theorem, and Wilson’s theorem. Our goal is not only to solve problems but also to cultivate a deeper appreciation for the elegance of mathematical concepts.

We encourage readers to actively engage with the material, to explore beyond the solutions provided, and to discover the joy of uncovering truths for themselves. In preparing this book, we have drawn upon a wealth of sources, including classic texts and contemporary research, to ensure a comprehensive and enriching experience.

We are grateful to the many mathematicians whose work has inspired and informed these pages, and we hope to pass on a fraction of their passion for number theory to our readers. Whether you are embarking on this journey out of curiosity, academic interest, or the pursuit of mathematical beauty, we welcome you.

May this book serve as a valuable resource and companion as you explore the intriguing world of elementary number theory. .