It's unloaded RPM, no prop.
'calc programs like Pcalc at
www.flydma.com, or Motocalc at
www.motocalc.com, are useful tools for getting an idea of how a power system will behave under load. I ran the numbers on Pcalc, and there's no way that the motor will handle a 5x5 prop direct drive:
44 Amps [X(]
Prop RPM is also only about 26000, but pitch speed is 123MPH. Still, the motor will burn up in a few seconds with 44 Amps flowing through it. Heat won't be an issue because the windings will burn out long before the motor has a chance to get hot...