The database version (db_version in wp_option) is 7558.
See WordPress 2.5 Theme Compatibility and Plugin Compatibility to confirm the theme and plugins you’re using are compatible.
- PHP 4.3 or greater (old requirement was PHP 4.2 or greater).
- Administration Panels redesign (see WordPress Interface Guidelines)
- Widget-based dashboard
- You should be able to have any number of any widgets
- Search for both posts and pages (#1435)