The fifth Fermat number is composite

Proved

WorkbookSource.plus_32274

by wamlart · Sep 12, 2026 · Mathlib 0df444a (Lean v4.33.1)

lean-workbooksource-checked

Prove that $2^{32} + 1$ is not a prime number. (no calculators allowed)

Source: InternLM Lean-Workbook, record lean_workbook_plus_32274 (Apache-2.0). Complete source proposition preserved; proof developed independently.

Preamble

import Mathlib
open Real Nat

Formal statement

theorem WorkbookSource.plus_32274 : ¬Nat.Prime (2^32 + 1)   :=  by sorry

Source