Okay learned a little about age 20 according to Jewish traditions. The age of majority is not designated in biblical literature, but it's basically the standard for taxation (e.g., Exodus 30:14) and conscription (e.g., Numbers 1:3, 24). This age seems to apply equally to males and to females (see Leviticus 27:4-7), but only for taxation. 

Moral responsibility age seems to begin at age 20. In Numbers, God distinguishes those of age 20 and above, guilty of mutinous, faithless complaints, from "your little ones" and "your children," who alone will arrive in the Land of Israel as promised (Numbers 14:26-35). So the age of 20 marked the transition to adulthood in the biblical period, even though no ceremony seemed to mark it as the age of such.