Common errors in Spanish - Numbers
I think students of all foreign languages find learning numbers to be somewhat of a chore, but with some persistence, they're not that hard to learn in Spanish, except for "quince" (15) and "quinientos" (500) which seem to be everyone's least favorite numbers. Aside from that, I've noted four common errors that students make with the numbers in Spanish:
1. "un mil"
It is never, ever "un mil" - it's one word: "mil": mil perros (a thousand dogs), mil paraguas ( a thousand umbrellas), mil alumnos ( a thousand students).
2. "un millón dólares / dos millon dólares"
First, it's always "un millón DE" whatever you are talking about: un millón de dólares (a milion dollars), un millón de personas ( million people), un millón de problems (a million problems).
Second, after "un millon", it's always "millones": dos millones de dólares (two million dollars), tres millones de personas (three million people), veinte millones de problemas (twenty million problems).
3. "treinta y uno años"
The numbers ending in "some number and one", when preceding a masculine noun, change "uno" to "un": tengo treinta y un años (I'm 31 years old), tengo ciento y un caballos (I have 101 horses).
4. "Doscientos mujeres"
I bet you didn't even spot the error on this one! In the hundreds, when the noun the number modifies is feminine, the hundreds number is feminine as well: doscientas mujeres (200 women), quinientas flores (500 flowers), mil seiscientas mesas (1600 tables).
Hope this helps / Espero que esto ayude