How dense would something have to be to create a black hole big enough to destroy Earth?

Question: How dense would something have to be to create a black hole big enough to destroy Earth?
- Keywords:
  black hole,
  cosmology
Asked by anon-187123 to Miriam on 16 Nov 2018.
- Miriam Hogg answered on 16 Nov 2018:
  
  You would need something with the mass of 3 Suns in the space less than the size of Earth to make a stable black hole. The center of the black hole is theoretically infinitely dense but we aren’t sure if it would be in real life. It would be very high density though. Something like that would be relatively small (the radius of Earth, maybe even smaller) but would easily tear up the Earth.

Question: How dense would something have to be to create a black hole big enough to destroy Earth?