Radiators and heating costs

I have a huge radiator in the stairwell of my 3 family. I basically can’t turn it off, so when the heat goes on for the building it always starts up. This is good in the sense that it heats the common hallway for the second and third floors, but I have to ask… Is it necessary for me to heat the common hallway? People get their mail on the first floor which isn’t helped by the radiator. Is there some benefit to the overall heating level of the building? Do you think it’s worth the cost to cap off this radiator to save in heating costs? I wonder how much one big radiator contributes to the overall heating costs, which of course are very high. Thoughts? Thanks.