The calculated distance (air line) between Düsseldorf and Katwijk aan Zee is approximately 122 miles respectively 197 kilometers.
By car or train, the actual journey to Katwijk aan Zee is certainly longer, as only the direct route (as the crow flies) between Düsseldorf and Katwijk aan Zee has been calculated here.
Air line (approximately)
197 kilometers
106 nautical miles