Number Theory – Classical Foundations and Modern Perspectives offers a broad, up-to-date view of one of the central areas of pure mathematics, highlighting its deep theoretical roots and expanding role in modern science. Bringing together diverse perspectives, the volume explores classical themes such as prime numbers, divisibility, and structural aspects of number theory alongside contemporary developments in computational and algorithmic number theory. Particular attention is given to emerging applications in areas including post-quantum cryptography, discrete structures, signal analysis, and interdisciplinary modeling, illustrating how number-theoretic ideas continue to inform current research and technological challenges. In addition to research-oriented contributions, the book addresses reflective and educational dimensions, examining the nature of proof, the communication of mathematical ideas, and innovative approaches to teaching fundamental number-theoretic concepts. By combining classical foundations with modern methodologies, computational tools, and pedagogical perspectives, this edited volume provides a coherent and multifaceted picture of number theory as a dynamic and evolving discipline. Designed for researchers, graduate students, and educators, the book serves as both a reference to current trends and a resource for understanding the enduring relevance of number theory across mathematics, computation, and education.