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.
▸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
- EvenEven
def
- PerfectNat.Perfect
def
▸Related work0
▸For your AI
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.
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