Upgrading My Late Model 2013 IMAC to Monterey

I currently have a 27" IMAC in perfectly good condition with a Quad Core 3.5 ghz processor with 32 gigs of Ram, 2TB Serial ATA Drive+256GB SSD. Would it be possible to download the Monterey software and upgrade my machine? It seems fully capable of updating to the new software and yet Apple won't let me upgrade. What can I do? This machine works great and is very fast with no issues at all. How can I work around this issue?