The Erdös Number Project

This is the website for the Erdös Number Project, which studies research collaboration among mathematicians.

The site is maintained by Jerry Grossman, Professor of Mathematics Emeritus at Oakland University. Please address all comments, additions, and corrections to Jerry at

Erdös numbers have been a part of the folklore of mathematicians throughout the world for many years. For an introduction to our project, a description of what Erdös numbers are, what they can be used for, who cares, and so on, choose the “Information about the Erdös Number Project” link below. To find out who Paul Erdös is, look at this biography at the MacTutor History of Mathematics Archive, or choose the “Information about Paul Erdös” link below. Some useful information can also be found in this Wikipedia article, which may or may not be totally accurate.


  • Information about the Erdös Number Project: General overview, including our (admittedly arbitrary) rules for what counts as a research collaboration.

  • The Erdös Number Project Data Files: Lists of all of Paul Erdös’s coauthors and their respective coauthors, organized in various ways. There are also links to websites of or about Erdös’s coauthors.

  • Facts about Erdös Numbers and the Collaboration Graph: Statistical descriptions of Erdös number data, a file of the sub graph induced by Erdös coauthors, Erdös number record holders, facts about collaboration in mathematical research and the collaboration graph, including some information about publishing habits of mathematicians (for example, the median number of papers is 2, and the mean is about 7). This subpage has loads of information about the collaboration graph and Erdös numbers, including the distribution of Erdös numbers (they range up to 13, but the average is less than 5, and almost everyone with a finite Erdös number has a number less than 8) and “Erdös numbers of the second kind”.

  • Some Famous People with Finite Erdös Numbers: Fields Medalists and Nobel Prize winners have small Erdös numbers.

  • Computing Your Erdös Number: It may be smaller than you think.

  • Research on Collaboration in Research: Papers on collaboration in scientific research, collaboration graphs and other small world graphs, and Erdös numbers. A lot of research is currently being done by various scientists on collaboration graphs and related topics.

  • Information about Paul Erdös (1913–1996): Information about and links to books, films, articles, memorials, reminiscences.

  • Publications of Paul Erdös: They continued to appear more than ten years after his death.

  • Items of Interest Related to Erdös Numbers: Six degrees of separation, the Kevin Bacon game, Small Worlds, academic genealogy, Hank Aaron, graph theory, and other miscellany.

This website is the successor to the Erdös Number Project website hosted by Oakland University, which is scheduled to be closed by the university at some point. If anyone has information that might improve the accuracy of this site, such as published articles that I am unlikely to be aware of, or the fact that an Erdös coauthor has died (or, as Paul Erdös would say, “has left”), please let me know. The data currently shown on this site are based primarily on all items appearing in MathSciNet and DBLP through mid-2020. About 1600 new people with Erdös number 2 were added in this quinquennial update.

This page was last updated on January 4, 2022 (but subpages may have been updated more recently).