Pulling from my own experience, short stories are easier to sell in the 1500 to 2500 word range, though I have sold stories that were shorter and stories that were longer.
As most published short stories wind up in magazines, stories of this length fit well on a page with a picture and a short introduction, which is why the 1500 to 2500 word length is favored.
Regardless, if your story needs more words then write it with more words. There's always a chance you can cut some words in your final revision and if it stays longer there are publications out there that will publish a longer story.
I hope this helps. :)
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