It seems an unlikely pairing. One was the most prominent mathematician of antiquity, best known for his treatise on geometry, the Elements. The other was the most prolific mathematician in history, the man whom his eighteenth-century contemporaries called “analysis incarnate.” Together, Euclid of Alexandria (c325–c265 BC) and Leonard Euler (1707–1783), born in Switzerland and at various times resident in St. Petersburg and Berlin, collaborated on proving an interesting result in number theory–without the benefit of e-mail or time travel.
Mathematician William Dunham describes this remarkable effort, which spanned nearly 20 centuries, in his book Euler: The Master of Us All.