On Nov\'ak numbers
  In this work, we obtain some new lower bounds for the number $\mathcal N_B(x)$ of Nov\'ak numbers less than or equal to $x$. We also prove, conditionally on Generalized Riemann Hypothesis, the upper estimates for the number of primes dividing at least one Nov\'ak number and give description for the prime factors of Nov\'ak numbers $N$, such that $2N$ is a Nov\'ak-Carmichael number. 
Alexander Kalmynin
math.NT