LOL
Let's change it a little bit. The number is 710 to put Navcorr out of my misery. It has one number: 627 4387 so the only valid 710 coded number is 710-6274387
If you dial that number, you'll get a beep. You'll then need to enter a 12 digit PIN to get any further. Then you'll be able to dial any other number.
Guesses as to why this exists and what you'd use it for?
HINT: It's not live sex lines for Trump, nor is it to get toll free calls, although that might well be a by product.
Further HINT: You might want to look at a US phone keypad
I'm going offline for platelet donation in about 2 hours, so if no one gets it I'll reveal the answer and nominate the best answer
C