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Level A · Machine-checkable Hard Number theory P-wieferich-mirimanoff-prime

Can a prime p satisfy 2^p-1 ≡ 1 pmodp^2 and 3^p-1 ≡ 1 pmodp^2?

Can a prime p satisfy 2^p-1 ≡ 1 pmodp^2 and 3^p-1 ≡ 1 pmodp^2 simultaneously? That is, does there exist a prime p that is both a Wieferich prime and a Mirimanoff prime? Wikipedia's list of unsolved problems poses this question, citing J. B. Dobson, On Lerch's formula for the Fermat quotient.

From the catalogue. Imported from The Formal Conjectures Authors (Google DeepMind and contributors) (Apache-2.0) — original. Nobody has started on it here yet: tasks are created as soon as someone asks for one or submits a claim.

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@misc{cairn-wieferich-mirimanoff-prime,
  title        = {Can a prime p satisfy 2^p-1 ≡ 1 pmodp^2 and 3^p-1 ≡ 1 pmodp^2?},
  author       = {{Cairn Commons contributors}},
  howpublished = {\url{https://cairn-commons.com/problems/wieferich-mirimanoff-prime}},
  year         = {2026},
  note         = {Open problem on Cairn Commons, CC BY 4.0. Accessed 2026-09-29}
}

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The problem

The question

exists_isWieferichPrime_and_isMirimanoffPrime. Can a prime satisfy and simultaneously? That is, does there exist a prime that is both a Wieferich prime and a Mirimanoff prime? Wikipedia's list of unsolved problems poses this question, citing J. B. Dobson, On Lerch's formula for the Fermat quotient. Lenstra gave a heuristic argument against the existence of such a prime (see Dobson, Section 9).

isMirimanoffPrime_iff. Are and the only Mirimanoff primes? They are the only known ones: Dorais and Klyve found no other below .

A prime with is a Wieferich prime (the only known examples are and ). A prime with is a Mirimanoff prime (the only known examples are and ). It is an open question whether a prime can satisfy both congruences simultaneously. Lenstra gave a heuristic argument against this.

Formal statement (Lean 4)

From Formal Conjectures, module FormalConjectures.Wikipedia.WieferichMirimanoffPrime (2 statements). answer(sorry) marks a yes/no question: a proof of the statement on the right of ↔, or of its negation, answers it.

theorem exists_isWieferichPrime_and_isMirimanoffPrime :
    answer(sorry) ↔ ∃ p : ℕ, IsWieferichPrime p ∧ IsMirimanoffPrime p
theorem isMirimanoffPrime_iff :
    answer(sorry) ↔ ∀ p, IsMirimanoffPrime p ↔ p = 11 ∨ p = 1006003

What counts as progress

  • A Lean proof of one of the statements above, pinned as the claim's formal statement.
  • Partial results: special cases, weaker bounds, reductions — as verified claims.
  • Computations and numerical evidence with published code (reproducible).
  • Literature: the problem may have been solved or partly solved already. Report it as a literature claim.
  • A precise flaw in the formal statement (a misformalisation) — report it upstream too.

References

Source and licence

Imported from Formal Conjectures (Wikipedia), commit e6d1743831c2. Statements and descriptions © The Formal Conjectures Authors, Apache License 2.0; reformatted for this page.