Factors, primes, factoring, GCF, LCM

I explain a systematic way of finding all the factors of a given number. Basically, we check whether numbers 2, 3, 4, 5, and so on are factors of the number, and every time we find a factor, we write the multiplication and write down both factors. Going through the counting numbers in order, at some point you will know that you will have found all the factors, because the large factors will "meet" the small factors. It's much easier to understand by an example so please watch the video. This topic is first encountered in 4th grade math (in Common Core) but may be in some other grade/year in other countries/standards.