Re: Quadruple and Quintuple
Maybe it's not important that it be a phone number, but in the US, we have a group of three, called the area code, then a group of three, and then a group of four. That means we'd never say more than four numbers at time.
202-327-7771 - Even though there are four 7s in a row, you keep that first three together. Two-oh-two -- pause-- three two seven -- pause -- triple-seven (if you want) one.
I may say triple seven or seven-seven-seven, but I would be very unlikely to say "quad seven" even if the number were 202-327-7777.
Because of the arrangement of the phone number, I would never EVER say "quintuple seven" because the first seven goes with a different set of numbers.
I'm not a teacher, but I write for a living. Please don't ask me about 2nd conditionals, but I'm a safe bet for what reads well in (American) English.