check out
http://processing.org/reference/nfs_.html

That's what I need, but can I keep the number as an integer?

You don't need integer data for display, since that's what you asked. You keep the integer data in the original variable, and exploit the result of nfs() in the display part.

That is blindingly obvious - why didn't I see that?!? Thanks anway.

No problem, sometime we focus on a thing and miss the simple solution.
Just a word of warning: in Java/Processing, if you write literally 017, it won't give the result you expect. Because of C language roots, this number is interpreted as an octal number! So a 018 will actually generate a syntax error...