Erdös Number
My Erdös number is 6 because I have co-authored with Ian C.W. Hardy, who has co-authored with Tim Blackburn, who has co-authored with John H Lawton, who has co-authored with Joel E Cohen, who has co-authored with Ronald L Graham, who has co-authored with Paul Erdös himself.
Mathematical Genealogy
In terms of mathematical genealogy, it appears that I am one of the thousands of distant descendants of Sir Isaac Newton. The ancestral path from Newton to me goes through Roger Cotes, Robert Smith, Walter Taylor, Stephen Whisson, Thomas Postlethwaite, Thomas Jones, Adam Sedgwick, William Hopkins, George Gabriel Stokes, John William Strutt (Lord Rayleigh), J.J. Thomson, G.I. Taylor, Michael Glauert and David Acheson. So there is a sense in which my Newton number is 15: in terms of the student-advisor relationship, Newton is my great-great-great-great-great-great-great-great-great-great-great-great-great-grandfather.