We have physical sensors to understand the world around us. While we have settled down on sight, sound, taste, smell, touch; I am sure there are many direct and indiect sensors in our body connected to the brain. For example, pressure, temperature, flow and others.
The sixth sense could be considered a derived knowledge from multiple sensors. It is similar to understanding what is solid or liquid from just vusual imagery.
You could similarly have seventh sense, eight sense and so on....a derived sense from the database...