Is the gcf of an odd and even number is always even

The greatest common factor of an odd and even number won't always be even-in fact, they are always odd. If the even number is 6 and the smaller number is 3, then the gcf will be 3. If the even number is 28 and the smaller number is 21, then the gcf is 7. If the even number is 48 and the odd number is 21, then the gcf would be 3. Also, if they are prime, the gcf would be one, an odd number. 

Answer\ __o_o__/ lil i don’t kniw