The Ancient Egyptians believed in One God

 who was self-produced, self-existent, immortal, invisible, eternal, omniscient, almighty, etc. This One God was never represented. It is the functions and attributes of his domain that were represented. These attributes were called the Neteru. The term, gods, is a misrepresentation of the Egyptian term, Neteru.
The name “God” does not tell us anything. One can only define “God” through the multitude of its attributes, qualities, powers, and actions. However, once we describe the attributes and qualities, we then begin to know what it is. A person who is an engineer, a father, a husband, … etc. does not have poly-personalities, but rather a mono-personality with multiple functions/attributes. For the Ancient and Baladi Egyptians, the concept of God is similar. These attributes, for example are: (Isis), (Osiris), Amen, (Horus), Mut, etc., became the symbols of such attributes, functions, forces, and energies. Each deity served a unique function.
To know god is to know the numerous qualities. The more we learn of these qualities(known as Neteru), the closer we are getting to our divine origin. Far from being a primitive, polytheistic form, this is the highest expression of monotheistic mysticism.