The commission may hear and determine an application, and approve, disapprove, or require modification of a plan submitted under section 521.3 without notice and without public hearing. The commission may require a public hearing when necessary to conserve the interests of the members, policyholders, or shareholders of the affected company. In such cases the commission shall require the affected company to mail to all of its members, policyholders, or shareholders written notice of the public hearing stating that an application and plan have been filed with the commission, the nature of the plan, and the date, time, and place of the public hearing on the application and plan. The commission shall determine the number of days prior to the public hearing that notice is required to be given to the members or shareholders, which shall be no fewer than ten nor more than sixty days.