Lowest Common Multiple
The Lowest Common Multiple (LCM) of two or more given numbers is the lowest (or smallest or least) of their common multiples.
Ex.:     Find the LCM of 24 and 90. 
Sol.:     The prime factorisations of 24 and 90 are:
            24 = 2 × 2 × 2 × 3; 90 = 2 × 3 × 3 × 5
        In these prime factorisations the maximum number of times the prime factor 2 occurs is three; this happens for 24. Similarly, the maximum number of times the prime factor 3 occurs is two; this happens for 90. The prime factor 5 occurs only once in 90.
Thus, LCM = (2 × 2 × 2) × (3 × 3) × 5 = 360