Both, autogamy and geitonogamy are prevented in

Autogamy involves pollination within the same flower, while geitonogamy involves transfer of pollen grains from the anther of one flower to the stigma of another flower of the same plant. Both the processes are prevented in papaya because it is a dioecious plant (i.e., male and female sex organs are borne on separate plants) and it always needs cross-pollination.