Rembrandt took on an unusually high number of apprentices in order to insure him a significant income. Some of these apprentices were sufficiently talented as to emulate Rembrandt's own painting and their best works are arduous to distinguish from Rembrandt's own. His work was also imitated by other talented painters as well both during and after Rembrandt's lifetime.
Among all the portraits of Rembrandt, self portraits play an very important role. The large amount of his self portraits is the most among all the painters in history. According to incomplete statistics, the self portraits of Rembrandt stored in museums all over the world are around 90, 60 of them are oil painting, 20 of them are Copper Etching, 10 are pencil sketch self portrait. According to his later encounter and the fact of his selling off his property, probably other self portraits are missing in personal hands. There was a theorist calculating that every single year, Rembrandt would paint two self portrait. As a result, the total amount of Rembrandt's self portraits is over 100.