2. (8 points) There is a type of cell, every hour 2 cells die, and the remaining cells each split into 2. If after 5 hours the number of cells is recorded as 164. How many cells were there at the beginning?
9
【Answer】Solution: At the beginning of the 5th hour, there are: $164 \div 2+2=84$ (cells) At the beginning of the 4th hour, there are: $84 \div 2+2=44$ (cells)

At the beginning of the 3rd hour, there are: $44 \div 2+2=24$ (cells)
At the beginning of the 2nd hour, there are: $24 \div 2+2=14$ (cells)
At the beginning of the 1st hour, there are: $14 \div 2+2=9$ (cells)
Answer: At the very beginning, there were 9 cells.
Therefore, the answer is: 9.