Elementary closed-forms for non-trivial divisors
Abstract
We present several elementary closed-forms that express a non-trivial divisor for every composite integer . Each closed-form consists of a fixed number of elementary arithmetic operations drawn from the set: addition, subtraction, multiplication, integer division, and exponentiation. Two families of closed-forms are developed. First, direct application of the hypercube method yields closed-forms , , , and expressing the smallest prime divisor, largest non-trivial divisor, largest prime divisor, and greatest prime , respectively. The factorial-unwinding technique underlying these hypercube constructions leads to extreme symbolic complexity, motivating our main result: An alternative closed-form that avoids factorial-unwinding by synthesizing the quadratic residue invariants (largest such that is a divisor) and (number of distinct prime divisors) with integer root extraction. Although evaluating these closed-forms requires exponential time, the number of arithmetic operations performed remains constant and independent of the input size . This sharply contrasts with traditional algorithmic methods, where the number of operations required to locate a non-trivial divisor necessarily scales with .
Cite
@article{arxiv.2510.26939,
title = {Elementary closed-forms for non-trivial divisors},
author = {Mihai Prunescu and Joseph M. Shunia},
journal= {arXiv preprint arXiv:2510.26939},
year = {2025}
}