Theorem 4nprm

Description: 4 is not a prime number. (Contributed by Paul Chapman, 22-Jun-2011) (Proof shortened by Mario Carneiro, 18-Feb-2014)

	Ref	Expression
Assertion	4nprm	⊢ ¬ 4 ∈ ℙ

Proof

Step	Hyp	Ref	Expression
1		2nn	⊢ 2 ∈ ℕ
2		1lt2	⊢ 1 < 2
3		2t2e4	⊢ ( 2 · 2 ) = 4
4	1 1 2 2 3	nprmi	⊢ ¬ 4 ∈ ℙ