An insurer formed in this state shall be either
(1) An incorporated stock insurer, or
(2) An incorporated mutual insurer, or
(3) An incorporated specific risks mutual property insurer, or
(4) An incorporated mutual assessment property insurer only, or
(5) An incorporated farm mutual assessment property insurer only, or
(6) A reciprocal insurer, with respective powers, duties, and restrictions as provided in this code.