7 pages, new proposition 3, many correctionsLet P be the set of all primes and ψ(n)=n∏n∈P,p∣n(1+1/p) be the Dedekind psi function. We show that the Riemann hypothesis is satisfied if and only if f(n)=ψ(n)/n−eγloglognn0=30 (D), where γ≈0.577 is Euler's constant. This inequality is equivalent to Robin's inequality that is recovered from (D) by replacing ψ(n) with the sum of divisor function σ(n)≥ψ(n) and the lower bound by n0=5040. For a square free number, both arithmetical functions σ and ψ are the same. We also prove that any exception to (D) may only occur at a positive integer n satisfying ψ(m)/m<ψ(n)/n, for any $