(the first one if more chained)
$ openssl x509 -in certfile.pem -noout -text
$ openssl x509 -in certfile.pem -noout -pubkey
Options:
-noout: do not print the PEM itself (the input)
-text: print full details; -pubkey: print PEM public key
$ openssl rsa -in pubkey.pem -pubin -noout -text
$ openssl rsa -in privkey.pem -noout -check