The capital stock shall be divided into shares of a stated par value. No business shall be transacted by the corporation until the whole amount of its capital stock is subscribed for and actually paid in in cash. No stock shall be issued by any corporation until the par value thereof shall be fully paid in in cash. Any corporation may, subject to the approval of the State Bank Commissioner, increase or reduce its capital stock in the manner hereinafter provided. In the case of a reduction, the capital stock shall not be reduced to less than the amount required by § 1645 of this title.