DIOPHANTUS, a celebrated mathematician of Alexandria, reputed to have been the inventor of algebra. When he lived, is not known: some have placed him before Christ, and some after, with equal uncertainty. He wrote 13 books of arithmetic; which, the astronomer Regiomontanus tells us, are still preserved in MSS. in the Vatican library: Meziriac's edition of seven of these books has been several times reprinted, with notes and illustrations.