Where to download calculator app for MacOS?

I am looking for where the Calculator app for Mac OS can be downloaded. I don't see it on the AppStore. I'm pretty sure it came installed on my iMac. I only see it for the iPhone and watch but even then I'm not sure it's the same. Might mine be a carry over from an earlier OS? I checked an mine is an Apple piece of software. I see now it can't even be deleted so my friend (for whom I'm searching) should have it on their computer??