"Have one number" can be antonymized in various ways depending on different senses we are speaking of. If we are speaking of the sense of having one number singularly, an antonym could be "multiple numbers," "varied numbers," or "numerous numbers." However, if we are speaking of "having one number" as an idiomatic expression for being honest, antonyms could be "deceitful," "insincere," or "dishonest." The word "have one number" can also be interpreted as being stuck in one position or having one perspective, and antonyms might include adaptability, flexibility, or open-mindedness. Ultimately, the antonym of "having one number" depends upon the context in which it is being used.