I know that stiffness, K is equal to product of moment of inertia and square of natural frequency
K = Jωn2
Where K = stifness, J = moment of inertia and ωn = natural frequency
SI unit of J is kg m2, while SI unit of ωn,natural frequecny is rad/s but as shown in attached snap, SI unit of K is (Nm)/rad. I have tried to solve and simplify the product of units of J and ωn2, but I am unable to understand how we get unit of K as (Nm)/rad because I get units as (Nm)rad2.