23569920

Appears in sequences

• Multiply-perfect numbers: n divides sigma(n).at n=11A007691
• 4-perfect (quadruply-perfect or sous-triple) numbers: sum of divisors of n is 4n.at n=3A027687
• Multiply perfect numbers whose average divisor is an integer and divides the number itself.at n=5A046985
• Intersection of A046985 and A033950: multiply perfect, refactorable numbers with integer average divisor dividing the number.at n=3A047728
• Numbers m such that m = sigma(abs(k)) - 3k, where k = sigma(m) - 3m.at n=8A069146
• Numbers k such that sigma(k)/k and sigma_3(k)/k are both integers.at n=9A076233
• Multiply perfect numbers k for which the quotient sigma_5(k)/k = A001160(k)/k is nonintegral.at n=2A088845
• Numbers k that divide (sum of proper divisors of k + product of proper divisors of k).at n=11A089748
• Numbers k such that S(S(k))=k, with S(n)=sigma(n)/4: 1/4-sociable numbers of order 1 or 2.at n=7A113286
• Let S(n)=sigma(|n|)-3*n; sequence gives numbers n such that S(S(S(S(n))))=n. May be called {3,1}-Sociable number of orders 1 or 2 or 4.at n=14A114528
• Multiply perfect numbers k such that sigma(k)/k > 2.at n=6A166069
• Bi-unitary multiperfect numbers.at n=19A189000
• Numbers n such that gcd(sigma(n), n) > gcd(sigma(m), m) for all m < n.at n=23A216793
• Numbers n with the property that, if tau(n) = k = number of divisors of n, and the d(i) are the divisors [arranged in increasing order], then the sum 1/d(k) + 1/d(k-1) + 1/d(k-2) + ... + 1/d(q) is an integer for some q.at n=25A226476
• Numbers n such that Sum_{i = 1..q} 1/d(i) is an integer where d(i) are the divisors of n for some q and n is primitive (the set {d(1), d(2), ..., d(q)} appears only once).at n=35A226853
• Numbers k that divide 3*sigma(k).at n=29A245774
• Numbers m such that k(m) = m/tau(m) - sigma(m)/m is an integer.at n=5A245778
• Refactorable multiply-perfect numbers.at n=3A245782
• Numbers n such that k(n) = (n/tau(n) + sigma(n)/n) is an integer.at n=4A245786
• Numbers n such that tau(n)*sigma(n) divides n^2.at n=6A245787