You could also (in theory) put every human on Earth in Texas with a population density of only 26,000 people per square mile, about the same density as New York City.
If you removed the empty space in our atoms, you could fit all humanity into a unit roughly the size of an m&m.
That's nothing, I swear the entire planet squeezes into a mile long stretch on 93 in Boston every weekday around 5:30 pm.
If it's an equilateral square pyramid, the volume would be about a quarter of a cubic kilometer. If we assume humans have an average mass of 65 kg and the same density as water, that gives us room for just under 4 billion humans.