From the Gospel Coalition:
Do you know how many prayer are mentioned in the Bible (and how many were answered)? Here’s the answer to that question and other things you should know about the prayer in the Bible.
1. There are 650 prayers listed in the Bible. (Here is the entire list and where they can be found.)
2. There are approximately 450 recorded answers to prayer in the Bible.
3. The first time prayer is mentioned in the Bible is Genesis 4:26 (earlier dialogues where initiated directly by God, e.g., Genesis 3:8-13, Genesis 4:9).
4. The Bible records Jesus praying 25 different times during his earthly ministry.
read the rest here.