This book arose from a course of lectures given by the first author during the winter term 1977/1978 at the University of Munster (West Germany). The course was primarily addressed to future high school teachers of mathematics; it was not meant as a systematic introduction to number theory but rather as a historically motivated invitation to the subject, designed to interest the audience in number-theoretical questions and developments. This is also the objective of this book, which is certainly not meant to replace any of the existing excellent texts in number theory. Our selection of topics and examples tries to show how, in the historical development, the investigation of obvious or natural questions has led to more and more comprehensive and profound theories, how again and again, surprising connections between seemingly unrelated problems were discovered, and how the introduction of new methods and concepts led to the solution of hitherto unassailable questions. All this means that we do not present the student with polished proofs (which in turn are the fruit of a long historical development); rather, we try to show how these theorems are the necessary consequences of natural questions. Two examples might illustrate our objectives."

This book arose from a course of lectures given by the first author during the winter term 1977/1978 at the University of Munster (West Germany). The course was primarily addressed to future high school teachers of mathematics; it was not meant as a systematic introduction to number theory but rather as a historically motivated invitation to the subject, designed to interest the audience in number-theoretical questions and developments. This is also the objective of this book, which is certainly not meant to replace any of the existing excellent texts in number theory. Our selection of topics and examples tries to show how, in the historical development, the investigation of obvious or natural questions has led to more and more comprehensive and profound theories, how again and again, surprising connections between seemingly unrelated problems were discovered, and how the introduction of new methods and concepts led to the solution of hitherto unassailable questions. All this means that we do not present the student with polished proofs (which in turn are the fruit of a long historical development); rather, we try to show how these theorems are the necessary consequences of natural questions. Two examples might illustrate our objectives."

Dieses Buch ist aus einer Vorlesung entstanden, die vom ersten der bei- den Verfasser im Wintersemester 1977/78 an der Universitat Munster ge- halten wurde. In dieser Vorlesung, die sich vor allem an Lehrerstuden- ten wandte, ging es nicht so sehr urn systematische Wissensvermittlung, sondern darum, Interesse an zahlentheoretischen Fragestellungen und Entwicklungen zu wecken, wobei vor allem historische Zusarnrnenhange in den Vordergrund gestellt wurden. Bei dieser Zielsetzung ist auch das Buch geblieben, das keines der vie len vorhandenen ausgezeichneten Bu- cher uber Zahlentheorie ersetzen kann oder will. Wir versuchen, an aus- gewahlten Beispielen zu zeigen, wie aus der Untersuchung naheliegender zahlentheoretischer Probleme im Laufe der geschichtlichen Entwicklung irnrner umfangreichere und tiefere Theorien entstanden sind, wie irnrner wieder neue unerwartete Zusarnrnenhange zwischen scheinbar ganz verschie- denen Problemkreisen entdeckt wurden und wie die Einfuhrung neuer Metho- den und Begriffe oft die Losung lange Zeit unangreifbar erscheinender Probleme ermoglichte. Wir wollen also einige wichtige Satze der Zahlen- theorie den Studierenden nicht als fertiges Ergebnis in einer Formulie- rung und mit Beweisen, die Endprodukte einer langen Entwicklung sind, vorsetzen, sondern wir versuchen darzustellen, wie sich diese Satze notwendig aus naheliegenden Fragestellungen ergeben haben.