No even number gose in 21. In fact there is none that goes in 21, either.
21 is an odd composite number
an odd number
An even number can be divided by 2 evenly. An odd number will have a remainder of 1 when divided by 2. 21 is an odd number.
20 is even number.
21+9=20
It is odd.
because in a mean for 7 with three numbers the total of the 3 numbers must be 21 and (even number) + (even number) = (even number) 21 is odd Q.E.D
22.
Forty-two.
21 is the composite number because it's an odd number. 2 cannot be a composite number because it's even.
I would say 21, because it is not an even number like the rest are.