What are all the factors of 21?

With alll of except for the 2 that i did already

The radius of the circle below intersects the unit circle at (3/5,4/5). what is the approximate value of theta? 0.6 radians 1.0 radians 36.9 degrees 53.1 degrees

Let f(x) = 5/x and g(x)=2x2+5x. what two numbers are not in the domain of f o g