Centos iptables open port 53
Your semantics are reversed.
The rules you posted permit outgoing DNS connections to a remote DNS server, not incoming connections to a local DNS server.
To permit connections to your local DNS server, reverse the INPUT and OUTPUT rules:
-A INPUT -p udp -m udp --dport 53 -j ACCEPT
-A OUTPUT -p udp -m udp --sport 53 -j ACCEPT
(And please take a few minutes at some point to revise your firewall to be stateful.)
Use -I instead of -A .
As you have a DNS server listening then it will be listening on port 53 so the input rule should be
-I INPUT -p udp -m udp --dport 53 -j ACCEPT