It looks more like a 39 under certain enlargement, and the top of the number in question looks flat. The 1909 wheats I’ve found also “corrode” in a different way than wheats past the 20’s for some reason, the older ones seem to hold up a lot better and just turn a funny “pea green”. It’s tore up anyway, just brush it.
Take it in a dark room and shoot a flashlight across the coin so you get shadows. I think it's too crusty to see though. I've found so many wheaties as of late that, if they're bad, I'll take some lemon juice and a toothbrush. I have every Philly from 1909 to 1935 so I tend to not be as careful as I once was. Unless they're pitted really bad they clean up nice then I hit them with Mother's Mag and Uluminum polish. Again, I have plenty with the original patina.