Skyscrapers is a noun. It's the plural form of skyscraper.
No, the noun 'skyscraper' is not a standard collective noun. However, collective nouns are an informal part of language, any noun that suits the context of the situation can function as a collective noun; for example, a skyscraper of bureaucrats, a skyscraper of commerce, a skyscraper of excess, etc.
The average height of a story in a skyscraper is 8 to 10 feet, depending on what part of the world it is built in. The average total height of a skyscraper will also vary depending on what region it is in.
The part of speech for this particular word is a noun.
part of speech
The part of speech for "answer" is a noun.
adverb
what part of speech is beneath
The part of speech for "unfamiliar" is an adjective.
The part of speech of "came" is a verb.
The part of speech for "twirl" is a verb.
The part of speech for "explicit" is an adjective.