The calculated distance (air line) between An Muileann gCearr and Athlone is approximately 26 miles respectively 41 kilometers.
By car or train, the actual journey to Athlone is certainly longer, as only the direct route (as the crow flies) between An Muileann gCearr and Athlone has been calculated here.
Air line (approximately)
41 kilometers
22 nautical miles