is 201-40 a featherweight? I bought a box of attachments and inside I found the original sales receipt for the machine it says its a 201-40. Can anyone tell me what kind of machine it is

A 201 is Singer's premium machine. It is far from a FW. It is a full size machine with excellent sewing capabilities. What is the serial number of the machine you purchased? The Singer dating site will tell you what it is, minus a few whose records were lost. Singer kept good records.

FWs are 221s and 222s only.

I've heard (but this is just something I read) that the 201 is the best machine Singer made.
I have one and love it! Glad you have one :)

I didn't buy it, it was nowhere to be found at this estate sale but I found and bought the accessories box and the original recipt was in that box. Are they worth more than featherweights?

Oh, I thought you bought it.
FW's sell for a lot more than the 201's.
As for "worth" I don't know. I just know what they sell for :)
I love both!

are the attachments interchangable with Featherweights?

I have been told that they are interchangeable, I have a 201K and a 222K, I just tried the hemmer from the FW on the 201 and it fits. They are both short shank machines.