English

Elementary closed-forms for non-trivial divisors

Number Theory 2025-11-03 v1

Abstract

We present several elementary closed-forms that express a non-trivial divisor for every composite integer n>1n > 1. 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 T1(n)T_1(n), T2(n)T_2(n), T3(n)T_3(n), and T4(n)T_4(n) expressing the smallest prime divisor, largest non-trivial divisor, largest prime divisor, and greatest prime n\leq n, respectively. The factorial-unwinding technique underlying these hypercube constructions leads to extreme symbolic complexity, motivating our main result: An alternative closed-form T(n)T(n) that avoids factorial-unwinding by synthesizing the quadratic residue invariants χ(n)\chi(n) (largest rr such that r2r^2 is a divisor) and ω(n)\omega(n) (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 nn. This sharply contrasts with traditional algorithmic methods, where the number of operations required to locate a non-trivial divisor necessarily scales with nn.

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}
}
R2 v1 2026-07-01T07:14:40.139Z