I don't know but I always sort of had the impression that the .apk file for an app was like the .exe file for a program on a PC -- if it's not there, the program doesn't work. I wouldn't delete it; I think it IS the app. 
Hmmm. I'm not sure where you're gettting your .apk files; mine all have real names....there are one or two I'm not really sure what the app is, but that's not because it's a number, it's just that I can't remember downloading the app. But the rest have pretty clear names.SheilaJ said:Thanks Betsy. I've learned a long time ago to always backup before hitting that delete key. Too bad the .apk files don't have names to match the apps. Most are something like 234jjakjajsl.apk and you don't have a clue what it is for. There is probably a way to find this out and rename them but I don't know how to do it.