R = 2GM/C2

But when I compare my answers to sample question problems, I am consistantly getting different answers.

For example

A black hole with M (solar) = 3.7 x 10^6M

I plug in:

(2x(6.67x10^-11)(3.7 x 10^6))/(3x10^8)^2

But the answer I get is: 5.48e-21

The sample problem says it should be: 0.08 au or 16R

I have the same issues with every other one too

And it doesn't matter what I do -whether I convert Msolar to KG or try to break down the equation further, I still get different answers to those provided.

I am not sure where I am going wrong.