15
4,6,8,9,10,12,14,15,16,18 :)
15 and 9 are both odd, composite numbers less than 20.
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15 is a composite number - it can be divided by 3 and 5. 11, 13, 17 and 19 are all prime numbers, not composite.
would it will be 15
wowo is it a composite number dang how did I not see that...
The pairs are odd/even and prime/composite. For example, 9 is both odd and composite, whereas 2 is even and prime. (2 is the only even prime.) However, 20=22*5 is composite because it has factors other than itself and one. It is also even, aka not odd, as it has a factor of 2.
9 and 15 are the only two odd composite numbers less than twenty.
Is { 0, 20 } closed under multiplication
the composite number is 23
20 is a composite number. Its factors are 1, 2, 4, 5, 10, and 20.
The next composite number after 20 is 21.