We counted to 20 in ASL, let's keep going!
21 - Palm facing away from your body, index finger pointed up, thumb extended, other fingers closed. Bend the thumb a few times.
22 - Palm facing down, index and middle finger pointed away from your body, holding them a little apart. Bend them down once, then move your hand to the right and bend them down again.
23 - Palm facing away from your body, index finger, middle finger and ring finger extended, bend the middle finger a few times.
24 - Palm facing away, index finger and thumb extended, other fingers closed. Then put all four fingers up and close the thumb.
25 - Palm facing away, hand open with fingers a little apart. Stick out the middle finger and bend it a few times.
26 - Palm facing away, index finger and thumb extended, other fingers closed. Then put all four fingers up and touch the thumb to the pinky.
27 - Palm facing away, index finger and thumb extended, other fingers closed. Then put all four fingers up and touch the thumb to the ring finger.
28 - Palm facing away, index finger and thumb extended, other fingers closed. Then put all four fingers up and touch the thumb to the middle finger.
29 - Palm facing away, index finger and thumb extended, other fingers closed. Then put all four fingers up and touch the thumb to the index finger.
Here is a helpful video to show how these signs are done.
Numbers 1 to 30 | ASL - American Sign Language - ASL THAT

(from: wikipedia - american sign language)
Italian: ventuno, ventidue, ventitré, ventiquattro, venticinque, ventisei, ventisette, ventotto, ventinove
German: einundzwanzig, zweiundzwanzig, dreiundzwanzig, vierundzwanzig, fünfundzwanzig, sechsundzwanzig, siebenundzwanzig, achtundzwanzig, neunundzwanzig
Spanish: veintiún, veintidós, veintitrés, veinticuatro, veinticinco, veintiséis, veintisiete, veintiocho, veintinueve
French: vingt et un, vingt-deux, vingt-trois, vingt-quatre, vingt-cinc, vingt-six, vingt-sept, vingt-huit, vingt-neuf