The recent question about the most prolific collaboration interested me. How about this question in the opposite direction, then: can anyone beat, amongst contemporary mathematicians, the example of Christopher Hooley, who has written 91 papers and has yet to coauthor a single one (at least if one discounts an obituary written in 1986)?

Lucien Godeaux wrote more than 600 papers and not one of them is a joint paper. He cowrote a textbook in projective geometry. Mathscinet records only 15 citations to all these papers! But there is something called Godeaux surfaces which is mentioned in the literature. This is about the weirdest example I know. http://www.ams.org/mathscinet/search/author.html?mrauthid=241534 


How about Marina Ratner. I believe she has had no collaborators. 


I always like William Veech (57 papers) although it's unlikely, he will catch up. But his citation count is higher (after mathscinet). 


Leopold Vietoris (18912002) wrote more than 70 papers, only one of them with a coauthor see here. 


Until well into the 20th century, collaboration was more the exception than the rule among mathematicians. As an example, define the Betti number as the distance to Enrico Betti in the collaboration graph. Well, it seems that your Betti number is infinite (unless you are Enrico Betti): indeed, according to the link below, Betti is an isolated point in the collaboration graph: http://quod.lib.umich.edu/cgi/t/text/textidx?c=umhistmath&idno=AAN8909 

