LCM of 14 and 21 by prime factorisation.

 Solution:

LCM of 14 and 21 is the smallest number among all common multiples of 14 and 21.

14 = 21×71

21 = 31×71

LCM of 14 and 21 can be obtained by multiplying prime factors raised to their respective highest power.

=> 21×31×71 = 42

Hence the LCM of 14 and 21 is 42.