The full verse is

For to us a child is born,
to us a son is given;
and the government shall be upon his shoulder,
and his name shall be called
Wonderful Counselor, Mighty God,
Everlasting Father, Prince of Peace.

The verse is clearly a prophecy of the Messiah, fulfilled by Jesus Christ. Yet it applies the titles “Mighty God” and “Everlasting Father” to Jesus although the titles are elsewhere used only of God.

Despite the commonly believed doctrine of the Trinity, the Bible does not teach that Jesus is equal with God. Instead, it consistently refers to him as “Son of God”. Even for those who believe in the doctrine of the Trinity, the verse is difficult to understand because Jesus is not the Father but the Son.

However, the word “God” does not necessarily mean the Almighty Creator. Even humans were sometimes called “gods” (e.g., Psalm 82:6) meaning powerful people, but not equal with the Creator. Jesus is a mighty God without being the Almighty God. And the word “father” does not mean Jesus is equal with his father. “Father” is often used in the Bible to mean a leader. For example, Paul says  to the Corinthians “For I became your father in Christ Jesus through the gospel.” (1 Corinthians 4:15). Jesus is the father of the age to come (which is how the Greek Old Testament translated Isaiah 9:6).

Furthermore, Jesus is not the only one to be called by the names of God. In the Old Testament the angel who speaks for God is frequently addressed as God or speaks as God (e.g., Exodus 13:21; 23:21-22, Judges 2:1, 13:21-22). A person or being perfectly representing God, or standing in the place of God (e.g., Moses in Ex. 4:16, 7:1) can be called by the names and titles of God.

For more information, see Christ in the Old Testament or Jesus: God the Son or Son of God?.