Prime factorization of 144 and 180 is (2 × 2 × 2 × 2 × 3 × 3) and (2 × 2 × 3 × 3 × 5) respectively. As visible, 144 and 180 have common prime factors. Hence, the HCF of 144 and 180 is 2 × 2 × 3 × 3 = 36....
HCF of 16 and 27 is the largest possible number which divides 16 and 27 without leaving any remainder. The methods to compute the HCF of 16, 27 are explained here.