> quattuor et viginti

These are cardinal numbers: they can function like adjectives, in that they can directly modify substantive noun-like heads as attributes, except that they often have no adjectival endings. So this phrase is best considered an attributive phrase modifying *annos*.

In the broadest sense, the main clause is the entire sentence. In the narrowest sense, it is only *"Interea ad Hispanias P. Cornelius Scipio mittitur"*, though what follows is an appositive (*"filius..."*) to *"P. Cornelius Scipio"*; you might consider appositives as such to be part of the constituent they are apposed to.

> vir Romanorum omnium et sua aetate et posteriore tempore fere primus

This is a second appositive to *"P. Cornelius Scipio"*.