This is a feature of the Apple Card, visible only in the Apple Wallet under 'Card Info'. Dunno what banks other than Goldman Sachs would have to do.Is this true for [non-Apple] cards or only for banks that enable it? I am unable to find this number on my cards, all of which are from Chase. I'm using iOS 12.4.1.
The most detailed description I've seen of these Apple Card features is from last March at its announcement: How Apple Card Works (TechCrunch.com)