I think I will skip the part about being important. There is a formulation by Nicolas of a simple condition that is equivalent to RH and involves primorials, so it is easier to compute with than Robin's Criterion; Robin was his student.
There is a real number calculated in the criterion of Nicolas that is, as far as anyone has computed, strictly increasing as we got through the primorial numbers. Later, however, Planat et al showed that strict increasing forever would disprove Cramer's conjecture. Meanwhile item 84 in NICOLAS
PLANAT
Let's see, taking consecutive primorials $P,$ the function that, so far, keeps growing is
$$ \frac{e^\gamma \; \log \log P \; \; \phi(P)}{P}. $$
The really nice part is that we don't need to calculate $P$ itself. For each new prime factor $p,$ add $\log p$ to update $\log P,$ and multiply by
$$ \left( 1 - \frac{1}{p} \right) $$ to update
$$ \frac{\phi(P)}{P}. $$ By the time $p=211$ we have Nicolas' ratio reaching $0.97.$