From TFA:
> 2.43 kilometers a second, or 1.51 miles a second, or 5,400 miles an hour, or 8,700 kilometers an hour.
> There is, of course, no air and no sound on the Moon, so a "Mach number" doesn't really make sense. But if there were air, the speed would be about Mach 7, seven times the speed of sound.