Only 17% of all 64-bit Integers are products of two 32-bit integers
Summary
This article analyzes the fraction of 64-bit integers that can be written as the product of two 32-bit integers. It discusses hashing (clhash), a simple high-low hash, and the exact computation by Webster et al., concluding that about 17% of all 64-bit unsigned integers are such products and showing how to recover factors from a product.