"No.1" is a much more common spelling for this than "number 1", particularly "Number" spelled with a small "m".
My translation is a lot more ideomatic! When you see advertising, someone claiming to be the best, it will always be:
Continued from above (I did not mean to post, but to start a new line):
WE ARE NO.1!, never
We are number 1.
In this context, the "number would always be both capitalized and abbreviated. Please update your computer!