Is the word considered a noun?

No, the Word 'considered' is a verb, the past participle, past tense of the verb to consider; to think carefully about, in order to make a decision. The past participle of the verb also functions as an adjective.

Example:

He considered a trade school before applying to attend college. (verb)

This was the least expensive of our considered options. (adjective)

The noun forms of the verb to consider are considerer, consideration, and the gerund, considering.