Certain pages names (used in permalinks) are reserved for use by either WordPress or the theme and content model and should not be used as the single-word titles of any page at any level.
Reserved page names include:
In addition to these, WordPress will not allow page URLs containing only numbers, since it uses numeric URLs to distinguish posts from pages and would incorrectly try to parse the numeric URL as a date. If you have a page titled with a number, e.g. 2006, WordPress will automatically change its generated URL to
page-2006. You may edit the URL directly to something more appropriate, e.g.