It has often been asked if one is a prime number, or if there was a time when most mathematicians thought one was prime. Whether or not the number one is prime is simply a matter of definition, but definitions are often decided by the use of mathematics. In this paper we will survey the history of the definition of prime as applied to the number one, from the ancient Greeks to the modern times. For the Greeks the numbers (αριθμος) were multiples of the unit, and for this reason one did not fall into the category of primes (a subdivision of the numbers). This view held with few exceptions until Stevin (c. 1585) argued successfully that one was a number, at which point it finally made sense to ask if one is prime. This was followed by a period of confusion which began to dissipate with Gauss' Disquisitiones Arithmeticae. Our survey will show that for most of history, one was not considered a prime, and there was no point in time where a clear majority of mathematicians viewed one as prime.

Faculty Advisor Name

Chris K. Caldwell

Faculty Advisor Institution

University ofTennessee at Martin

Suggested Mathematics Subject Classification(s)

Primary: 11A51; Secondary: 11A51, 01A55


This work was supported in part by a College of Engineering and Natural Sciences undergraduate research grant. We thank our advisor Professor Chris K. Caldwell of the University of Tennessee at Martin and Professor David Broadhurst of Open University, UK, for their help in finding these sources.

Included in

Mathematics Commons



To view the content in your browser, please download Adobe Reader or, alternately,
you may Download the file to your hard drive.

NOTE: The latest versions of Adobe Reader do not support viewing PDF files within Firefox on Mac OS and if you are using a modern (Intel) Mac, there is no official plugin for viewing PDF files within the browser window.