I do not remember how I hade put it, so I can not erase...
I could not find in the help (italian)
Page numbers are on the Master Page.
Open the pages panel and the Pages at top of Panel = master pages!
Do you remove all page numbers or just a few?
Page numbres typically are on a master page, so I suggest you go to the master
page (in the Pages pallette). You should be able to erase it there.
Alternatively, if you want to erase the page number on just one page, hold control+shift while clicking on the page number. Then you can erase it.
Hope this helps,
("Master page"!! yes!!)