Looking for a SciFi short story, published in an anthology since 2000, which mentions "The Bulk" and also deals with prime numbers.
The story Artifacts by Stephen Baxter describes ten dimensional spacetime as the Bulk:
Joe said, “Our universe is like a snowflake in a storm, one among a myriad others, all floating around in a nine-dimensional continuum called the Bulk.
And it does mention prime numbers:
Symmetries! Symmetries of squares and cubes! Symmetries of primes and perfect numbers!
I read it in The Solaris Book of New Science Fiction volume 3, which was published in 2009 so it fits your time frame. However there are probably lots of other stories that fit your description so we'd need some more details from you to see if this is the correct story.