# A Guide to Elementary Number Theory

### By Underwood Dudley

Catalog Code: DOL-41
Print ISBN: 978-0-88385-347-4
Electronic ISBN: 978-0-88385-918-6
140 pp., Paperbound, 2009
List Price: $51.00 MAA Member:$38.25
PDF Price: \$25.00

Series: Dolciani Mathematical Expositions

A Guide to Elementary Number Theory is a 140-page exposition of the topics considered in a first course in number theory.  It is intended for those who may have seen the material before but have half-forgotten it, and also for those who may have misspent their youth by not having a course in number theory and who want to see what it is about without having to wade through a traditional text, some of which approach 500 pages in length.  It will be especially useful to graduate student preparing for the qualifying exams.

Though Plato did not quite say, “He is unworthy of the name of man who does not know which integers are the sums of two squares” he came close.  This Guide can make everyone more worthy.

Introduction
1. Greatest Common Divisors
2. Unique Factorization
3. Linear Diophantine Equations
4. Congruences
5. Linear Congruences
6. The Chinese Remainder Theorem
7. Fermat’s Theorem
8. Wilson’s Theorem
9. The Number of Divisors of an Integer
10. The Sum of the Divisors of an Integer
11. Amicable Numbers
12. Perfect Numbers
13. Euler’s Theorem and Function
14. Primitive Roots and Orders
15. Decimals
17. Gauss's Lemma
18. The Quadratic Reciprocity Theorem
19. The Jacobi Symbol
20. Pythagorean Triangles
21. x4 + y4 ≠ z4
22. Sums of Two Squares
23. Sums of Three Squares
24. Sums of Four Squares
25. Waring’s Problem
26. Pell’s Equation
27. Continued Fractions
29. Carmichael Numbers
30. Sophie Germain Primes
31. The Group of Multiplicative Functions
32. Bounds for π(x)
33. The Sum of the Reciprocals of the Primes
34. The Riemann Hypothesis
35. The Prime Number Theorem
36. The abc Conjecture
37. Factorization and testing for Primes
38. Algebraic and Transcendental Numbers
39. Unsolved Problems
Index

### About the Author

Underwood Dudley received the Ph.D. degree (number theory) from the University of Michigan in 1965.  He taught at the Ohio State University and at DePauw University, from which he retired in 2004. He is the author of three books on mathematical oddities, The Trisectors, Mathematical Cranks, and Numerology all published by the Mathematical Association of America.  He has also served as editor of the College Mathematics Journal, the Pi Mu Epsilon Journal, and two of the Mathematical Association of America’s book series.

### MAA Review

Everyone who studies and does mathematics needs, every once in a while, to study or remember some facts of fundamental mathematics, and there is no doubt that we cannot except results and facts of number theory. The main motivation of the author of this book is to provide a friendly volume in response to that need. In fact, the book under review is a concise and useful review of the facts of elementary number theory. It covers most required topics of elementary number theory, and also some strange topics like “Decimals” and “Multigrades,” which are not often found in similar books. Continued...

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