Spanish Numbers

Numbers in Spanish are always singular. Plural forms of numbers don't exist. Look at the examples below. The noun is plural (houses, children, friends), but the number is not (five, ten, three).

cinco casas - five houses
diez niños - ten children
tres amigos - three friends

The number "one" has both a masculine and a feminine form "uno" and "una". For example:

sólo un amor - just one love
sólo una noche - just one night

Other numbers do not change for gender.