The calculated distance (air line) between Montreuil and Le Blanc-Mesnil is approximately 5 miles respectively 8 kilometers.
By car or train, the actual journey to Le Blanc-Mesnil is certainly longer, as only the direct route (as the crow flies) between Montreuil and Le Blanc-Mesnil has been calculated here.
Air line (approximately)
8 kilometers
5 nautical miles