1021019

Properties

Appears in sequences

• Primes of the form primorial P(k)*2^n-1 with minimal n, n>=0, k>=2.at n=5A103515
• Primes of the form primorial P(k)*n-1 with minimal n, n>0, k>=2.at n=5A103783
• Sophie Germain primes that are also highly cototient numbers.at n=35A209194
• Conjoined Twin Primes: primes p such that p written in base 10 has a prefix q and a suffix r, where q and r are a pair of twin primes (in either order), and q and r overlap (i.e., strlen(q)+strlen(r)>strlen(p)).at n=3A250052
• (Twice product of first n primes) - 1.at n=7A282704
• Smallest prime factor of A282704.at n=6A282705
• Square array A(n,k) = A276945(n,k)-1, read by descending antidiagonals: A(1,1), A(1,2), A(2,1), A(1,3), A(2,2), A(3,1), etc.at n=38A286615
• Transpose of square array A286615.at n=42A286616
• Numbers k such that phi(sigma(k))/k < phi(sigma(m))/m for all m < k, where sigma is the sum of divisors function (A000203) and phi is Euler's totient function (A000010).at n=42A293711
• Numbers k where records occur for phi(k)/phi(k+1), where phi is the Euler totient function (A000010).at n=36A335070
• Prime numbersat n=80051