Starting with WordPress 2.5, there is a bug where you cannot have a child Page that’s stub is a number. For example this will not work: /about/5/. That URL conflicts with paged content feature where you can posts and Pages with multiple pages of content by adding <!--nextpage--> within your content.

This plugin allows you to have children Pages with numbers as stubs by giving up the ability to have paged Pages which isn’t a big deal as most people don’t use paged Pages anyway.

Plugin Page