My Japanese dictionary says "san" is another reading for and means "mount" as in Mount Fuji.
It's a deity with a Marine Corps base at the bottom. The Marines used to like to hike up with their bicycles on their backs and ride around the crater while I was huffing and puffing to make the top. I climbed it four times in the 80's and 90's. The biggest problem at the time was orange peels and empty cigarette packs, but it was a problem and it's been that way a very long time.
It's a crowded, touristy slog up a treeless volcanic peak (treeless past Station Five, anyway), but one time of the four I got lucky and was at the top to see sunrise on a clear morning. Asahi. Incredible sight.