I guess so. It has something to do with the Planck length.
However I read the Wikipedia article a bit more carfully now, and I found out that, if the assumption that there are small extra dimensions is true, then the minimum mass is only 1 TeV. Otherwise the LHC couldn't create black holes with its 14TeV.
This means you only need about 600 protons/nucleons. That's still more than an atom, but much less than my last number.

EDIT: (as you edited your post, too): I think Stephen Hawking proved that black holes do exist. But of course the current model isn't quite accurate, because in the center of a black hole the timespace warp is infinite and all phyisical laws are only valid under the assumption that it's amlost not warped at all.