Is a CPU fan speed of 3590 RPMs normal?

"73 degrees is a little high if you ask me. The RPM of your fan is determined by a host of things but ~4000 is fine I tend to like slower fans that move more air because they are quieter.
If the noise is bothering you buy a large fan/heatsink for $30-40 and replace it

EDIT: After seeing the pics... That looks like a stock CPU fan, I'd replace it with something quieter, it will bring the temp on your CPU down and be much quieter. When you pick something make sure it's going to fit. You don't have a whole lot of space between the CPU and the RAM"

"The speed of the fan is highly subjective to the controller regulating it, the type and model of the fan itself, or the load/temperature of the CPU.

From my experience, that speed is nothing out of the ordinary.

What kind of system is this running in? Is it an aftermarket CPU cooler or stock?"

If you're going to fly it's good to have over 3500RPM at least.