The Everything Engine is built from nodes, all the way down . 1 is the nodetype node - the node that defines what types (other) nodes can be. It itself is of the type nodetype, obviously. 2 is the container nodetype. 3 is the document nodetype...

There are some more nodetypes, but these all aren't for the gods alone to view - every pmdevil can look at these.

Of course, there is no significance that 23 is the lowest positive number accessible to the general public.