The least common multiple (LCM) is the smallest number that is a multiple of two numbers. The LCM of two numbers can be found by listing their multiples or using the prime factors method. The listing ...The least common multiple (LCM) is the smallest number that is a multiple of two numbers. The LCM of two numbers can be found by listing their multiples or using the prime factors method. The listing method involves writing out the multiples of each number until the first multiple common to both lists is found. The prime factors method involves writing each number as a product of primes, matching primes vertically when possible, and then multiplying the factors together to obtain the LCM.