The calculated distance (air line) between Deventer and Alphen aan den Rijn is approximately 64 miles respectively 104 kilometers.
By car or train, the actual journey to Alphen aan den Rijn is certainly longer, as only the direct route (as the crow flies) between Deventer and Alphen aan den Rijn has been calculated here.
Air line (approximately)
104 kilometers
56 nautical miles