I know that for an orthogonal matrix, i.e. a square matrix with orthonormal columns, the inverse is the transpose. What about the general case when the columns of a square matrix are non-zero and orthogonal, but not necessarily of length $1$? (The matrix is invertible since non-zero orthogonal vectors are linearly independent.) Is there a simple characterization/formula for the inverse, or a simple way to compute it?
What if we additionally require that the columns are orthogonal, and the rows are orthogonal? (I know there exist invertible matrices with orthogonal columns, but not orthogonal rows.)