There are well over 100 pyramids in Egypt. Those not belonging to Giza tend to be forgotten. Most of them are also in very bad condition and some of them are just piles of crumbled stone.
As most attention is given to the 2,2m building blocks of the Cheops pyramid and everyone is so busy with their calculators it's worth pointing out that at least ten times as many blocks were actually mined, transported and erected. What is not known is whether all these pyramids were just practice runs for Giza, which in total needed far more blocks than 2.2million.
The question of manpower raises serious concerns when taking all of the pyramids into the calculations. As the average life expectancy was probably about 25 years any male slave or worker could only give about ten years of his life to this work. And the workforce - as we understand it today - would have had to have been in tens and tens of thousands. All of whom had to be fed, housed and clothed.
Some sort of food and water source would have had to be near at hand and there would have to have been really large graveyards.
Not many remains of such large scale operations have been found - it does make one wonder.
https://www.youtube.com/watch?v=U21uaEVINCY