The calculated distance (air line) between Düsseldorf-Pempelfort and Mengenich is approximately 18 miles respectively 29 kilometers.
By car or train, the actual journey to Mengenich is certainly longer, as only the direct route (as the crow flies) between Düsseldorf-Pempelfort and Mengenich has been calculated here.
Air line (approximately)
29 kilometers
16 nautical miles