When someone says that "one's number is up," it means that the person's time is almost over, and they are about to face their end. There are numerous synonyms one can use to convey the same meaning. For example, "doom is approaching" or "the end is nigh" are alternative ways to express that someone is about to face a severe consequence. "The clock is ticking," "the wheels are in motion," or "the die is cast" also indicate that the time is running out, and a tragic event is inevitable. In general, these phrases indicate a sense of finality, indicating that there is no more time to change the course of events.
