How many null hypotheses are used in a 2 x2 factorial ANOVA?

In a 2 x 2 factorial ANOVA, there are three null hypotheses tested. These include one for each of the two main effects (one for each factor) and one for the interaction effect between the two factors. Therefore, you test the null hypothesis that each factor has no effect on the dependent variable, as well as the null hypothesis that there is no interaction between the factors.