Numeral
cincuenta
fifty
"Cincuenta páginas ocultaban una sola idea."
Fifty pages hid a single idea.
Write it
Write a sentence with cincuenta in it, whatever's on your mind.
It doesn't have to be perfect
Short story
A three-sentence story with cincuenta in it. New one every time.
Couldn't write one just now - try again in a moment.