letI H := IsCyclotomicExtension.zeta_spec p' ℚ (CyclotomicField p' ℚ)
p : ℕ
hpri : Fact p.Prime
p' : ℕ+ := ⟨p, ⋯⟩
this : Fact (↑p').Prime := hpri
⊢ Prime (⋯.toInteger - 1)
p : ℕ
hpri : Fact p.Prime
p' : ℕ+ := ⟨p, ⋯⟩
this : Fact (↑p').Prime := hpri
H : IsPrimitiveRoot (IsCyclotomicExtension.zeta p' ℚ (CyclotomicField p' ℚ)) ↑p' :=
  IsCyclotomicExtension.zeta_spec p' ℚ (CyclotomicField p' ℚ)
⊢ Prime (⋯.toInteger - 1)