14 (fourteen)

16 (sixteen)

16mm film

17 (seventeen)

18 (eighteen)

180

19 (nineteen)

1st (first)

1st-order [first-order]

2 (two)

2/3 (two thirds)

20 (twenty)

20/20 vision

20th century

21 (twenty-one)

21st century

22 (twenty-two)

23 (twenty-three)

24 (twenty-four)

24 hour(s) service

24 hours a day, seven days a week

24-pin plug

24/7

24/7/365

2nd (second)

2nd edition

2nd World War

2nd-best [second-best]

2nd-order [second-order]

2P (Two-Poisson model)