How big is the TP400-D6 turboprop installed on the A400M?
According to the MTU Aero Engines technical data of the TP400-D6:


  Propeller diameter: 209.8 in


(mtu.de)

That is a propeller diameter of 5.33m. I also could not find more details about the nacelles, but one can estimate the size from a photograph. I used this image from aviationtoday.com, which shows the aircraft from the front. With the known propeller diameter, I estimate the nacelle to be about 1.2m wide and about 1.85m high:



I don't think it is possible to derive more precise numbers due to the inaccuracies resulting from the perspective.