What Kind of Number is One?
Date: 12/06/2001 at 16:36:34 From: Mrs. Reed Subject: One, primes and composites What is one called since it is neither prime nor composite? I have tried numerous search engines and Web sites.
Date: 12/06/2001 at 20:45:56 From: Doctor Tom Subject: Re: One, primes and composites Hi, Usually it is called a "unit." In the integers, the number -1 is the only other unit. The primes are 2, 3, 5, ... and -2, -3, -5, ... Usually folks working with primes just use the positive integers, in which case 1 is the only unit. In more complex algebraic structures, there may be even more units. For example, in the Gaussian integers (which are complex numbers of the form: a + bi, where a and b are integers, the units are 1, -1, i, and -i. Note that 2 is no longer prime in the Gaussian integers: 2 = (1+i)(1-i). - Doctor Tom, The Math Forum http://mathforum.org/dr.math/
Search the Dr. Math Library:
Ask Dr. MathTM
© 1994-2015 The Math Forum