Connections between prime numbers and geometry This might be a little open-ended, but I was wondering: are there any natural connections between geometry and the prime numbers? Put differently, are there any specific topics in either field which might entertain relatively close connections?
PS: feel free to interpret the term natural in a broad sense; I only included it to avoid answers along the lines of "take [fact about the primes] $\to$ [string of connections between various areas of mathematics] $\to$ [geometry!]"

A simple example: number p>2 is prime iff any equiangular p-gon with rational side lengths is regular, see, e.g., http://www.cut-the-knot.org/Outline/Geometry/EquiangularP-gon.shtml
