A Primordial Black Hole the size of a single atom would weigh roughly 1 billion tons approximently the mass of a large mountain.
Small PBHs would actually disappearing! Due to Hawking Radiation, any PBH lighter than 1015 grams would have evaporated by now.
Some scientists believe the "missing" mass of the universe (Dark Matter) isn't a new particle, but just trillions of tiny PBHs floating in the void.
PBHs might be the "missing link" that explains how supermassive black holes existed only 500 million years after the Big Bang. They were born big!