Any tax due and unpaid under this part 2 shall be a debt to the state, and shall draw interest at the rate imposed under section 39-21-110.5, in addition to the interest provided by section 39-21-109, from the time when due until paid. The executive director of the department of revenue may recover at law the amount of such tax and interest in a suit instituted by the attorney general in the name of the executive director of the department of revenue, and this remedy shall be in addition to all other remedies.