What are the typical max range and max flight time (endurance) Mach numbers for the A320?
Max range, or Cost Index 0, actually has many Mach numbers depending on the weight, FL, and wind. Its range is from approximately Mach 0.57 to 0.78. Below is part of the relevant table from the FCOM (other intermediate weights are omitted):



The FCOM does not state a max endurance speed, just that in a hold, the FMS will fly the lowest of the "ICAO speed limits, the max endurance speed, or any speed constraint."

So the FMS will take care of calculating it, but like max range, it will vary.