What does the # symbol after an IP address mean?

I resolved an IP address from a URL using nslookup and noticed the following:

nslookup https://example.com

Server 192.168.3.214

Address 192.168.3.214#53

What does the #53 at the end mean?

Solution 1:

#53 refers to port 53, the standard port for DNS.

Solution 2:

In any event, the Address...#53 line refers to the server, rather than being an answer to the resolution request. Running the command on- as others have observed- an elderly server:

$ nslookup https://example.com
Server:         127.0.0.1
Address:        127.0.0.1#53

** server can't find https://example.com: NXDOMAIN

$ nslookup example.com
Server:         127.0.0.1
Address:        127.0.0.1#53

Non-authoritative answer:
Name:   example.com
Address: 93.184.216.34

There is obviously scope for confusion here because of # being used for anchors inside web pages. However OP should have taken that error message to heart and wondered what else wasn't working as he expected :-)