The calculated distance (air line) between Arrasate / Mondragón and Santutxu is approximately 25 miles respectively 40 kilometers.
By car or train, the actual journey to Santutxu is certainly longer, as only the direct route (as the crow flies) between Arrasate / Mondragón and Santutxu has been calculated here.
Air line (approximately)
40 kilometers
22 nautical miles