What does #53 mean in nslookup nameserver address result?

Question

When I run this:

nslookup some.host.com

I get results like this:

Server:         4.2.2.1
Address:        4.2.2.1#53

Non-authoritative answer:
Name:   some.host.com
Address: #.#.#.#

"4.2.2.1" is at the top of my /etc/resolv.conf, so that makes sense, but what does the #53 mean? Googling around, this seems to be commonly appended to the address here in nslookup results, but I can't find any information about what it actually means.

Answer 1

It's the port number used for DNS request.