Numbers

[Desmond]

Dos, Veintidós, Treinta y dos. Only 22 has accented ó

also 16 and 26 are accented 6 and 66 are not

[AngelicaDeAlquezar]

Is your question why?


The words that have only one syllable ("dos", "seis", "tres"...) do not bear a written accent unless their meaning could be confusing, like "sí"/"si", "él"/"el", "tú"/"tu", "se"/"sé", "mas"/"más"...


According to the syllable where they're stressed, Spanish has three kinds of words: agudas, graves/llanas, esdrújulas.

Palabras agudas: words that are stressed on the last syllable.
Palabras graves: words that are stressed on the second syllable, counting from the last one.
Palabras esdrújulas: words that are stressed on the third syllable, counting from the end of the word.


Written accent on palabras agudas: They end with n, s, or a vowel.
-> nación, compás, hindú...

Palabras agudas without a written accent: they end with any consonant, except n or s.
-> calor, formal, cabaret...


Palabras graves with a written accent: they end with any consonant, except n or s.
-> árbol, nácar, álbum...

Palabras graves without a written accent: they end with n, s, or a vowel.
-> examen, acentos, casa...


Palabras esdrújulas: They all bear a written accent.
-> brújula, atmósfera, pánico...


So "dieciséis", "veintidós", "veintitrés", "veintiséis" must have their written accent, as they are "palabras agudas" that have more than one syllable and that end with an "s".