The greatest common factor of 600 and 1050 is 150.
You can factor each: 600=100*6=2^2*5^2*2*3 = 2^3*5^2*3
1050=70*15=5*2*7*5*3=2*3*5^2*7
The greatest common factor is 2*3*5^2=6*25=150
Side Note: Usually, what say gcf instead of hcf, which means highest common factor. gcf is a more common way to say the factor that two numbers share that is greatest in value. gcf means greatest common factor.