Here are some examples:
* "Antidisestablishmentarianism" has the prefix "antidisestablishment-" which has four syllables.
* "Unforgettable" has the prefix "un-" which has one syllable, but the prefix "for-" in "forget" also has one syllable, resulting in a prefix with two syllables total.
While prefixes are typically shorter, there are exceptions where they can be longer and multi-syllabic.