55921

Properties

Appears in sequences

• Numbers k such that the continued fraction for sqrt(k) has odd period and if the last term of the periodic part is deleted the two central terms are both 31.at n=6A031619
• Primes with 21 as smallest positive primitive root.at n=7A061333
• Numbers n such that n, 10*n+1, 10*n+3, 10*n+7 and 10*n+9 are all primes.at n=18A067267
• Primes for which the smallest positive primitive root is odd and nonprime.at n=27A070269
• Numbers Sum_(j=1..k) sigma(j) / sigma(k) when this expression is an integer.at n=5A168128
• Prime partial sums of safe primes A005385.at n=7A172036
• Primes of the form pq + p + 1 where p < q are adjacent primes.at n=12A180932
• Primes of form a^2+b^2 such that a^4+b^4 and a^8+b^8 are primes.at n=38A182313
• Primes p such that 2*prime(p) + 1 = prime(q) for some prime q.at n=48A261361
• Primes p such that p+12, (p+1)/2, and (p+13)/2 are also prime.at n=21A283869
• Prime numbersat n=5676