Hola Beki, Yes you are correct.

Use cien when you are saying a hundred of something. Even if you want to say 100,000 it is “cien mil.” Unlike in English we don’t use the indefinite article “un” cien or “un” mil, but we do say “un” millón.

If you are going to use cien or cientos they are invariable; i.e. they will always be in the masculine e.g. la pagina cien, cien caballos, or cientos de mujeres. Finally you don’t say ciento y uno / una …… it would be ciento un, ciento una.  Thus ciento un pájaros; ciento una manzanas. 

You would only use the “y” between a unit of 10 and the single number. For example ciento veinte y dos = 122; doscientos/as ochenta y nueve = 289. You can see that the larger numbers follow the gender of the noun which they are describing. I hope that helps.

This lesson is worth reading: Numbers from 1,000 to 1,000,000 

If it doesn’t open just search for “large numbers”

Saludos. John