Ignoring all other considerations, one could produce a distance using the inverse square law.

Would that just mean taking the square root of the luminosity and interpreting it as distance in AUs?

So... https://www.google.com/search?q=sqrt%28420*10^12%29au+in+lig...

324 lightyears.

Assuming Sol habitable is 0.7 to 1.2au the translated would be 227 to 389. A shell of thickness approximately 160 light years where everything is in the habitable zone (as long as it is not too close to another heat source)