If a number P divides another number Q exactly, we say that P is a factor of Q i.e. Q is a multiple of P.
The H.C.F of two or more than two numbers is the greatest number that divides each of them exactly.
The least number which is exactly divisible by each one of the given numbers is called their L.C.M
Product of their H.C.F and L.C.M
Two numbers are co-primes if their H.C.F is 1.