No, port
13 and
37 are older simple time protocols.. these are offered by the
inetd(8) daemon and are enabled by default, there is no harm leaving them running.
How did you carry out this scan? if you're behind NAT these services will not be exposed publicly.. and by default, ports 25/587 (..smtp/sendmail) are bound only to localhost for logging and are not exposed over the network at all.
Port 6000 is for networked X connections, the default pf.conf blocks all non-localhost connections to this port (..actually, a range).. typically people use SSH now to do remote X as the protocol offers no encryption.
If you're receiving a lot of unsolicited traffic (..DoS) it will probably be ICMP packets, these are pretty much harmless to any modern OS, once upon a time legacy OS's had a very hard time dealing with specially crafted packets.. really though this is not a security risk anymore only a nuisance, and it happens all the time to everybody with a persistent connection to the Internet.