The phrase "am numerous" indicates that there are a large number of something. The antonyms of "am numerous" could be "am scarce" or "am few." These words indicate that there is a shortage or small amount of something. Another antonym could be "am singular," meaning there is only one of something. "Am rare" is another opposite that can be used to express that something is unusual or infrequently found. Additionally, "am solitary" could be used to describe something that is alone or without companions. These antonyms provide a contrast to "am numerous," indicating a scarcity or singularity of something.