552049

Appears in sequences

• Numbers whose sum of divisors is prime.at n=29A023194
• Numbers n such that n and sigma(n) are prime powers (of the form p^k, p prime, k>=1).at n=37A071114
• Prime powers of prime numbers such that the sum of its digits is also prime power of prime number.at n=28A076705
• Numbers k that require four iterations of the sigma function to be >= 2*k.at n=12A107914
• Irregular triangle in which row n has the values of k>1 such that sum_{i=n..n+k-1} i^2 is a square.at n=10A184885
• Odd numbers N for which numerator(sigma(N)/N) is a prime.at n=24A193065
• Numbers k such that tau(sigma(tau(k))) = sigma(tau(sigma(k))), where tau is A000005 and sigma is A000203.at n=19A237613
• Numbers n such that 2n-1 and sigma(n) are both primes.at n=16A249902
• Numbers n such that both sigma(n) and sigma(n) - 2 are primes.at n=10A274963
• Odd numbers with prime sum of divisors.at n=22A278911
• Numbers n such that the number of divisors of sum of divisors of n is prime.at n=39A281882
• Number of n X 6 0..1 arrays with every element unequal to 0, 1 or 4 horizontally, vertically or antidiagonally adjacent elements, with upper left element zero.at n=14A299593
• Numbers m such that m! / sigma(m) is not an integer.at n=30A325436
• Numbers k for which A348717(k) is a multiple of A348717(sigma(k)).at n=35A364131
• Powers p^m, with prime p and m > 1, such that neither p^m-1 nor p^m+1 are squarefree.at n=33A389960