An egg is the egg cell of a chicken, and there is only one egg cell, which is in the yolk. Egg yolk wraps egg cells and provides nutrition for the development of egg cells. Egg yolk contains no other cells except egg cells, and it is a mass of nutrients.
The main function of egg white is to balance and stabilize egg cells, make them "float" and provide the necessary water environment for the development of egg cells. Egg white also contains some nutrients, but much less than egg yolk. There are no cells in egg white.
Therefore, there is only one cell in an egg.