The calculated distance (air line) between Katwijk aan den Rijn and Nijmegen is approximately 66 miles respectively 105 kilometers.
By car or train, the actual journey to Nijmegen is certainly longer, as only the direct route (as the crow flies) between Katwijk aan den Rijn and Nijmegen has been calculated here.
Air line (approximately)
105 kilometers
57 nautical miles