As you know, the numbers follow the reverse gender up till ten: ثاثة رجالاث ث نساءFor 13 to 19 the first part of the number follows the opposite gender rule, but the عشرpart doesn’t. أربعة ا عشررجا أربع أة عشر إمرSame for the twenties etc… خمسة و ع شر ون ا رجا وأربعون تسع أة إمرFor eleven, both أحدand عشرare masculine when referring to masculine things, and only إحدىis feminine when referring to feminine things. Same thing for 21, and 31, etc… أحد عشر ا رجا أة إحدى عشر إمرSimilarly, for twelve, both ثنا اand عشرare masculine when referring to masculine things, and only إثنتاis feminine when referring to feminine things. Same thing for 22, and 32, etc…