Surely more support is needed to insert the beam that's going to hold up the end of the lintel after removing this one prop?Still just the one, if all you are doing is removing the end bearing. Other support may be necessary for other parts of the project.
One would only be OK for bricking it back up again, 3 or 5 if opening up the doorway - 2 or 4 more to support the wall above the doorway while opening outwards to get the new beam in.