A father tells his daughter of an invasion of the Earth by aliens who were "the greatest mathematicians in the galaxy":
(quoted from The Mathematicians)
"Go on, papa. These beings overran all Earth. Go on from there."
"You must know, these newcomers were vastly more intelligent than the Earthlings. In fact, the invaders were the greatest mathematicians in the System."
"What's the System? And what does mathematician mean?"
"The Milky Way. A mathematician is one who is good at figuring, weighing, measuring, clever with numbers."

The humans eventually triumph over these alien mathematicians by "imbuing these [aliens] with human emotions". Alien mathematicians are themselves a sort of stereotype (see here), but so is the idea that human mathematicians are cold and emotionless. So, arguably, this is a conflation of those two stereotypes. However, we do not see any direct evidence of their mathematical abilities or knowledge. So, despite the title, there really is not much math either implicitly or explicitly within this story.
The story ends with a Twilight Zonelike twist and a very corny math joke which really is the primary mathematical content.
It was originally published in the OctoberNovember 1953 issue of Amazing Stories and can now be found online for free at many locations including Gutenberg.org. 