From Useless Sexual Trivia: Tastefully Prurient Facts About Everyone’s Favorite Subject*:
“[T]he number of human ova necessary to repopulate the world could fit into a chicken egg.”
The human ovum appears to be roughly spherical:
The radius of an ovum is 0.12/2 = 0.06.
Applying the formula for volume of a sphere yields this.
This value converted from cubic centimeters to cubic millimeters:
50.95 cm^3 to mm^3 = 50,950 mm^3.
The volume of a human ovum divided into the volume of a chicken egg is this.
So, the number of human egg cells that can fit into a chicken egg is ~56,312,000.