God is omniscient and omnipresent. He hears EVERY prayer. He may not answer all prayers because He knows what we need. However, He obligates Himself to those of His children coming to Him through Christ. (Matthew 7:11; John 15:16; John 14:13-14; John 15:7; John 16:24).
John 9:31 - "We know that God does not listen to sinners, but if anyone is a worshiper of God and does His will, God listens to him.”
Also: Acts 10, Cornelius was of another religion (pagan seeking to know the God of the Jews) who prayed and God answered. God sent the Apostle Peter to tell him how to become Christian.
God will answer a prayer of anyone seeking to know Him.
As explained earlier, our Creator, God the Father hears every prayer. However He does not answer the prayers of sinners except their prayers for confession and repentance and their desire to stop sinning. People feel that sometimes when their prayers are not answered their prayers are not being heard by God. But the truth is their prayer is heard, but the answer of their prayer depends on the desire of their Creator.
If God answers their prayers immediately, He will, but sometimes, He has to keep silent until the right time to answer those particular prayers. God’s time is always the right time. We might be too impatient and ask Him to help or fearing that He is not hearing the prayers, but God answers the prayers when He knows is the right time.
We are human and can’t begin to know what God knows. Therefore, we will not know His reasons for delaying answers. We have to trust Him and be faithful that the answers will come. When we have faith, we might correct ourselves or issues involved in those prayer requests might correct themselves. Then these answers bring more benefits or blessings for everyone.
We all know that there is only One God who is the Creator of Heaven and Earth and that is God the Father. Who is also God of Abraham, Issac and Jacob. His ears are always ready to listen to the prayers of the righteous, according to Psalm 34:15, The eyes of the Lord are on the righteous, and His ears are attentive to their cry. This clearly states that He means our Creator heard the prayers of righteous or Holy people and believers.