The calculated distance (air line) between Hainburg an der Donau and Simmering is approximately 24 miles respectively 38 kilometers.
By car or train, the actual journey to Simmering is certainly longer, as only the direct route (as the crow flies) between Hainburg an der Donau and Simmering has been calculated here.
Air line (approximately)
38 kilometers
21 nautical miles