Nope. Soldered to the board - surface mount packages. The iMac is basically a laptop board in a desktop box - and yours isn’t a lot more serviceable than the very latest one, honestly.
The CPU is mounted in a Zero Insertion Force (ZIF) socket. If you (gently!) try to pull the CPU out of its socket, you will find that it does not budge. You first need to release the chip from the socket. Turn the screw on the CPU socket 180 degrees counter-clockwise to release the old CPU. Then pull up on the CPU chip to remove it.
https://www.ifixit.com/Guide/iMac+Intel+20-Inch+EMC+2105+and+2118+CPU+Replacement/35350