There are 19 Enochian Keys in the system of Enochian Magick. They are taken from the original Enochian language. (19 is a very important number, in many different magick systems)
However, the 19th Key is able to call upon any one of the 30 Aethyrs, by changing one word of the incantation. So, there are essentially 48 keys if this factor is considered.