391855697561 has 2 divisors, whose sum is σ = 391855697562. Its totient is φ = 391855697560.

The previous prime is 391855697551. The next prime is 391855697617. The reversal of 391855697561 is 165796558193.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 241985286400 + 149870411161 = 491920^2 + 387131^2 .

It is a cyclic number.

It is not a de Polignac number, because 391855697561 - 2³⁴ = 374675828377 is a prime.

It is a super-2 number, since 2×391855697561² (a number of 24 digits) contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (391855697551) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 195927848780 + 195927848781.

It is an arithmetic number, because the mean of its divisors is an integer number (195927848781).

Almost surely, 2^391855697561 is an apocalyptic number.

It is an amenable number.

391855697561 is a deficient number, since it is larger than the sum of its proper divisors (1).

391855697561 is an equidigital number, since it uses as much as digits as its factorization.

391855697561 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 61236000, while the sum is 65.

The spelling of 391855697561 in words is "three hundred ninety-one billion, eight hundred fifty-five million, six hundred ninety-seven thousand, five hundred sixty-one".