There's not really any such thing as an "apex datatype" - Oracle Application Express is a web application development tool built with Oracle PL/SQL, so it can be made to work (in various ways) with any datatype supported by Oracle SQL or PL/SQL.
In one sense, Apex only has one datatype - a VARCHAR2 string. Any number or date when bound to an Apex item will be converted (explicitly or implicitly) to a string.