Find the common factors of

$16$ and $18$

Q. find the common factors of 18 and 21

Q. Do as said for following numbers.
12, 16, 18
Factors of 12_______.
Factors of 16_______.
Factors of 18 _______.
Common factors of 12, 16, 18___________.
HCF of 12, 16, 18______________.

Q. Find the common factor of $16$ and $24$ and write the highest common factor $\left(HFC\right)$.