A brown dwarf is a deuterium-fusing substellar object, and, in the cases of the larger ones, a lithium-fusing one. They often emit electromagnetic radiation in frequencies that humans cannot see. However, the larger ones tend to emit visible light, if not much of it.
In this scenario, there's an Earth-sized body whose center is 2,000,000 kilometers from the center of a brown dwarf. Assume that the Earth-sized body is functionally identical to Earth in every way except for a lack of cloud cover.
How luminous does the brown dwarf need to be in order to illuminate the Earth-sized body with 0.5 lux/0.5 lumens per square meter of visible light at high noon? Assume that the Earth-sized body has an atmosphere identical to Earth's, except without cloud cover capable of reflecting said visible light.
Note that I'm not referring to radiant flux per unit area here here; radiant flux per unit area is the total of all electromagnetic striking a certain area, whereas I'm referring to luminous flux - that is, the amount of visible light striking a certain area. Certainly, there'll more energy striking the Earth-sized body then what's visible, but, in this question, I'm only referring to visible light.