The calculated distance (air line) between Düsseldorf and Castrop-Rauxel is approximately 33 miles respectively 53 kilometers.
By car or train, the actual journey to Castrop-Rauxel is certainly longer, as only the direct route (as the crow flies) between Düsseldorf and Castrop-Rauxel has been calculated here.
Air line (approximately)
53 kilometers
28 nautical miles