517661404440821 has 2 divisors, whose sum is σ = 517661404440822. Its totient is φ = 517661404440820.

The previous prime is 517661404440743. The next prime is 517661404440841. The reversal of 517661404440821 is 128044404166715.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 264188289976900 + 253473114463921 = 16253870^2 + 15920839^2 .

It is a cyclic number.

It is not a de Polignac number, because 517661404440821 - 2²² = 517661400246517 is a prime.

It is a super-5 number, since 5×517661404440821⁵ (a number of 75 digits) contains 55555 as substring. Note that it is a super-d number also for d = 3.

It is a Sophie Germain prime.

It is a Curzon number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (517661404440841) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 258830702220410 + 258830702220411.

It is an arithmetic number, because the mean of its divisors is an integer number (258830702220411).

Almost surely, 2^{517661404440821} is an apocalyptic number.

It is an amenable number.

517661404440821 is a deficient number, since it is larger than the sum of its proper divisors (1).

517661404440821 is an equidigital number, since it uses as much as digits as its factorization.

517661404440821 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 5160960, while the sum is 53.

The spelling of 517661404440821 in words is "five hundred seventeen trillion, six hundred sixty-one billion, four hundred four million, four hundred forty thousand, eight hundred twenty-one".