The papers comprising this volume explore various fields of number theory, including: the congruent property of solutions of quadratic Diophantine equations, K-groups over the ring of integers of number fields, L-functions of global function fields, automorphic forms, p-adic representations, and more. Applications of number theory, as in design and coding theory, are also explored. The research found in this volume can be seen as a reflection of the influence of Professor Keqin Feng upon the development of number theory studies in China, and this volume is therefore dedicated to him.Number Theory and Related Areas is a valuable reference for experts in these fields, as well as an excellent introduction for graduate students.