15857855

Appears in sequences

• Composite squarefree numbers k such that k^2-1 is divisible by p-1 and p+1, where p are all the prime factors of k.at n=27A306685
• Composite integers k such that sigma(k) | (k + 1)*tau(k) where tau is number of divisors of k.at n=28A384493
• Composite squarefree numbers k such that for any prime p dividing k both (p-1)/2 and (p+1)/2 divide k+1.at n=5A392557