Answer:
39 = 3 x 13
Explanation:
What are the factors of 39? How do we even do that?
We start at 2 and see if 2 will go into 39. It won't, so 2 isn't a factor.
Then we try 3. 3 goes into 39 thirteen times, so 3 & 13 are factors.
4 won't. And and in fact, no even integer will, because 2 won't.
Keep going up:
5? No.
Skip 6.
7? No.
9?
11?
13? Yes, we found that before, when we found 3.
So now we get to stop. 3 was the smallest factor that worked, and it was paired with 13, so that's the largest factor that will work. So no point in going on.
So what are ALL the factors of 39?
Just 3 and 13.
Now, are those PRIME factors? Yes, because nothing divides into them evenly; you can't factor them, so they're prime.
So now we can write 19 "as the product of prime factors":
39 = 3 x 13