What is the least natural number that is not a prime and not a factor of 80!?

The prime factors of 80 are 2, 2, 2, 2, 5, so any combination of these multiplied together is a factor of 80.  This means 2, 4 and 5 are factors.  3 is a prime number, so the first non-prime, non-factor is 6.

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3 is the first one........for 1 and 3 are the ways it can be divided,  and isn't a factor of 80

Oops!  Misread and duh on my part!