First, we find the possible candidates. Since the # can not be divisible by 2, there are no even # possibilities. This leaves 21. 23. 25. and 27. Since the # is not divisible by 3, that leaves the possibilities 23. and 25. 25 is divisible by 5, leaving the answer 23. To add on, 23 is not divisible by 4, assuring that it is correct.
23 people signed up for the chess club.
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