Which runway number do you select to "cross"

I always wondered which runway number to tell ATC to cross so like pretend for example San Diego… There is runway 27 and runway 9 but I have to cross it… Which number do I tell ATC? Thank you guys

I would say the active number but I’d like to know this answer as well

Whichever one is active. So if the operations are running from 27, you say 27 as well - regardless of where you are relative to start of it.

Conversely, for Unicom, any places with multiple runways and/or crossing runways, refer to the wind patterns. Whichever runway is green or amber will most likely be the active runway, or at least that’ll be the direction in which it’s likely to be used. Therefore use those numbers to communicate crossings to ATC and other aircraft