 In January 1999, while preparing some work for his students, he identified a highly structured prime number with exactly two thousand digits.Dubbing this prime a millennium prime, he wrote an email about it to a niece and nephew, which was subsequently published by Folding Landscapes, the publishing house of the cartographer Tim Robinson.He donated his author royalties to the Irish Cancer Society, and subsequently wrote an "Irishman's Diary" column about it for the Irish Times newspaper.