Comment by pnin

The senior title comes first -- Prof. Dr. Dr. Honorary doctorates are "honoris causa", abbreviated h.c. If you get multiple of these, you write Dr. h.c. mult. So you occasionally find Prof Dr. Dr. h.c. mult. X (would have been the correct way to address Umberto Eco, for instance). After introductions, people generally name only the most senior title, if any.