In the US, there is a number you need or you would not be able to buy or sell:
Without your social security number, you cannot get a job (oh, there are other ways to make money without the government knowing),
Having a “Job” is equal to “selling your services to an employer” - this is the selling you cannot do without a social security number.
And without an income you cannot buy food, clothing, housing, etc.
With a social security number, the US allows you to buy and sell.
It is a number on your forehead - you have it memorized (or most people do).
It is on your hand (in your hand) when you hand the card over to an employer so they can photo copy it for their employment records, and your hand “writes” (types) it when you do your taxes, etc.
As St. Peter in his first letter, St. Paul to the Philippians, St. Clement, and the writer to Diognetus, all remind us, we are aliens in the lands where we live, foreigners living in the midst of the peoples of the earth, citizens of a kingdom established by God, and being light and salt in the lands of our sojourning. We know about that other number, but it is not who we really are; we bear the mark of citizenship and sonship in the Kingdom of God.