The calculated distance (air line) between Düsseldorf and Monheim am Rhein is approximately 10 miles respectively 17 kilometers.
By car or train, the actual journey to Monheim am Rhein is certainly longer, as only the direct route (as the crow flies) between Düsseldorf and Monheim am Rhein has been calculated here.
Air line (approximately)
17 kilometers
9 nautical miles