Is 54 miles hyphenated as an adjective?

Here's why:

* Numbers over 20 are generally not hyphenated when used as adjectives.

* Numbers used as adjectives are typically hyphenated when they precede a noun (e.g., a twenty-mile hike). However, "miles" in this case is a noun, not an adjective.

Therefore, you would write:

* "They drove a 54-mile route." (Incorrect)

* "They drove a 54 mile route." (Correct)