The flowers on this last about a day once they've bloomed. It only started blooming in the last 2 years. First time, there was only a couple. Last year, there were quite a few. I keep it outside when the temp is above 70, and it seems to love it.
Here is what I've been able to find out so far, it is almost certainly some form of Echinopsis based on the shape, needles, and flower structure. Here is a direct quote from the website I used to identify it:
"The only cactus genus that is more confusing than Echinopsis is that of Opuntia. In both cases, there is a great number of species (over 100) and a tremendous amount of variation... The main factor that ties these plants together are their very large, showy flowers. These flowers are all very similar in structure – funnel shaped, with hairy/wooly scaled floral tubes... The flowers seldom last more than a single day and may be diurnal or nocturnal depending on the species. These species hybridize easily and have resulted in a tremendous number of hybrids..."
[url]https://cactiguide.com/cactus/?genus=Echinopsis[/url]
Oh well.

So far it looks like it's one of these two:
[url]https://cactiguide.com/cactus/?genus=Echinopsis&species=calochlora[/url]
[url]https://cactiguide.com/cactus/?genus=Echinopsis&species=arebaloi[/url]
Given the description of echinopsis, that may be as far as I get. C'est la vie.