With this applet you can investigate prime factors of integers (whole numbers) and also the HCF (Highest Common Factor), and the LCM (Least or Lowest Common Multiple) of two numbers.
You can also see how these things relate to each other, and get a fascinating insight into the behaviour of larger numbers.
[NB.The HCF is sometimes called the GCD (greatest common divisor).]

You can get the two numbers in two ways: either by entering them in the text boxes at the bottom of the page; or by using the random button at the top of the page - you can choose the maximum number of digits in the random numbers by entering a number from 1 to 7 in the "digits" box at the top of the page.
Play around. There's a great deal to learn about numbers from this applet.