Conjectura
Beta.Proofs cannot be submitted yet. The corpus is open to read, and we are looking for researchers to maintain a subject area.Maintaining a field →
← problemsNT012openMathematics/ Number theory

Are there odd perfect numbers?

Maintainer — open

A perfect number equals the sum of its proper divisors. Every one known is even. Nobody can rule out an odd one.

Motivation

Open since Euclid. Euler showed every even perfect number has the form 2^(p−1)(2^p − 1) with 2^p − 1 prime, which ties them to Mersenne primes exactly.

The odd case has accumulated an extraordinary list of necessary conditions — any odd perfect number exceeds 10^1500, has at least 101 prime factors counted with multiplicity, and at least 10 distinct ones — without anyone excluding it.

Open since Euclid, c. 300 BC.

Lean API
import Mathlib.NumberTheory.Divisors
import Mathlib.Algebra.Group.Even

namespace Conjectura.NT012

/-- No odd number equals the sum of its proper divisors. Open since antiquity; if one
exists it exceeds 10^1500. -/
def goal : Prop := ∀ n : ℕ, 0 < n → ¬ Even n → ¬ Nat.Perfect n

end Conjectura.NT012
Definition2
Related work0
    For your AI
    Download as .md
    I am proving a theorem in Lean 4 and submitting it to Conjectura.
    
    ## Problem NT012 — Are there odd perfect numbers?
    
    A perfect number equals the sum of its proper divisors. Every one known is even. Nobody can rule out an odd one.
    
    ## Environment (fixed — do not assume anything newer)
    
    - Lean toolchain: `leanprover/lean4:v4.33.0-rc1`
    - Mathlib: `v4.33.0-rc1`
    
    If a lemma you want does not exist in that Mathlib, prove it inline instead of
    importing something newer.
    
    ## The exact statement I must prove
    
    ```lean
    theorem solution : ∀ n : ℕ, 0 < n → ¬ Even n → ¬ Nat.Perfect n := by
      sorry
    ```
    
    ## The file I submit
    
    ```lean
    import Conjectura.Problems.NT012.Statement
    
    namespace Submission
    
    theorem solution : Conjectura.NT012.goal := by
      sorry
    
    end Submission
    
    ```
    
    ## The Lean definitions of every term in this problem
    
    These are the actual definitions your proof will be checked against. Do not
    substitute your own version of any of them.
    
    ### Even
    
    def
    
    ```lean
    Even
    ```
    Defined in Mathlib.
    
    ### Perfect
    
    def
    
    ```lean
    Nat.Perfect
    ```
    Defined in Mathlib.
    
    ## Rules — submissions violating these are rejected automatically
    
    1. **Do not change the name or type of `solution`.** It must satisfy the
       statement above exactly.
    2. **Do not redefine or shadow anything from the problem's Statement module.**
       Declaring your own `goal`, or redefining a name it depends on, produces a
       proof of a *different* statement and is rejected. This is the single most
       common rejection.
    3. **No `sorry`** anywhere, including in helper lemmas. It surfaces as the
       axiom `sorryAx` and is detected transitively through imports.
    4. **No `native_decide`** — it surfaces as `Lean.ofReduceBool` and is not
       accepted, because it trusts compiled code rather than the kernel.
    5. Only these axioms are permitted: `propext`, `Classical.choice`,
       `Quot.sound`.
    6. Follow Mathlib style: hypotheses left of the colon, explicit types,
       `snake_case` theorem names, `UpperCamelCase` types.
    
    ## What I want from you
    
    Here is my argument in informal mathematics:
    
    > [PASTE YOUR PROOF SKETCH HERE]
    
    Turn it into Lean 4 that compiles under the environment above and satisfies the
    statement exactly. Where you are unsure a lemma exists in this Mathlib version,
    say so explicitly rather than guessing a name.

    Submissions are not open yet

    Conjectura is in beta. You can read every statement, every definition and the Lean behind them, and download the exact files the checker uses — but proofs are not being accepted yet.

    The reason is a deliberate order of operations. Accepting a proof means running a stranger’s code and standing behind a verdict, and no statement here yet carries a researcher’s name. A machine-checked answer to a question nobody has vouched for is worth very little, so the vouching comes first.

    The English write-ups are also switched off during the beta. Nothing on this page is generated by a model.

    Discussion

    • Nothing yet.

    Sign in to take part.