5165160

Appears in sequences

• Smallest x such that sigma(x) = n*phi(x), or -1 if no such x exists.at n=21A055234
• a(n) = Min {x : sigma(x) = phi(n*x), x is not a prime}, least nonprime solutions to sigma(x) = phi(n*x).at n=22A087979
• a(n) = Min{x : sigma(x) = n*phi(x), x is not a prime}, the least nonprime solutions to sigma(x) = n*phi(x); special balanced numbers.at n=21A088830
• Numbers that can be expressed as the difference of the squares of primes in exactly twenty-one distinct ways.at n=1A092017
• Numbers with prime factorization pqrstuv^3.at n=18A190316
• a(n) is the least number k > 0 such that sigma(k) = phi(n*k).at n=22A256527
• Numbers n such that the multiplicative group modulo n is the direct product of 8 cyclic groups.at n=18A272598
• Balanced numbers (A020492) k with a record value of sigma(k)/phi(k).at n=12A335287