31998395520
domain: N
Appears in sequences
- Multiply-perfect numbers: n divides sigma(n).at n=20A007691
- 5-multiperfect numbers.at n=1A046060
- Multiply perfect numbers that are neither harmonic numbers nor arithmetic numbers.at n=3A046987
- Numbers n such that sigma(n) / n is prime.at n=12A065997
- Numbers k such that k divides DivisorSigma(2*j-1, k) for all j; i.e., all odd-power-sums of divisors of k are divisible by k.at n=6A066289
- Numbers k such that sigma(k)/k, sigma_3(k)/k and sigma_5(k)/k are all integers.at n=12A076231
- Numbers k such that sigma(k)/k and sigma_3(k)/k are both integers.at n=15A076233
- Numbers k such that sigma(k)/k, sigma_3(k)/k, sigma_5(k)/k and sigma_7(k)/k are all integers.at n=10A076234
- Multiply perfect numbers k such that sigma(k)/k > 2.at n=13A166069
- Nonprime numbers k such that k | (sigma(k) - Sum_{j=1..m}{sigma(k) mod d_j}), where d_j is one of the m divisors of k.at n=25A282775
- Multiply-perfect numbers m from A007691 such that m*(m-tau(m))/sigma(m) is not an integer where k-tau(k) is the number of the non-divisors of k (A049820) and sigma(k) is the sum of the divisors of k (A000203).at n=4A325024
- Multi-perfect numbers from A007691 that are not harmonic (A001599).at n=3A325026
- Multiply-perfect numbers m whose average divisor is not an integer.at n=12A330533
- Multiply-perfect numbers k that do not have a divisor d such that sigma(d)*d = k.at n=5A348032
- Numbers k for which k * gcd(sigma(k), u) is equal to sigma(k) * gcd(k, u), where u is obtained by shifting the prime factorization of k two steps toward larger primes [with u = A003961(A003961(k))].at n=24A349746
- Multiply-perfect numbers that are the sum of the divisors of some number.at n=19A354073
- Numbers k that have a record number of common divisors with sigma(k).at n=23A378267
- Multiperfect numbers k for which gcd(k,A003961(k))*gcd(sigma(k),A276086(k)) is not equal to gcd(k,A276086(k))*gcd(sigma(k),A003961(k)), where A003961(n) is fully multiplicative with a(prime(i)) = prime(i+1), and A276086 is the primorial base exp-function.at n=5A379492