A3. The Buddha taught that there are altogether 31 planes of existences; 4 are “lower” i.e. planes where the development is impossible (hell and animal planes, for example), 6 are the “heavenly” planes, and 20 are the “Brahma” planes (higher heavens still) plus the human plane.
 

For further reading see Chapter 9, Summary of Citta, Summary of Paramatthadhamma by Sujin Boriharnwanaket.