Typically, in a city government structure involving a council there is one councilman per city ward. Now a ward is a neighborhood or a collection of neighborhoods organized in a political district. The wiki has it that there are 19 named districts in Gotham so, assuming the wards are organized along the lines of the districts then that’ll mean they’re at least 19 but that may not be the case. Is there any indication to the exact number anywhere in the source material?