Language with the longest alphabet in the world is Khmer, the official language of Cambodia, with 74 letters. Khmer is an Austro-Asiatic language spoken by app. 12 million people.
Language with the shortest alphabet in the world is Rotokas, Eastern-Papuan language, with only 12 letters. Rotokas is spoken by app. 4,000 people in the island of Bougainville, in Papua New Guinea.