866642881021 has 2 divisors, whose sum is σ = 866642881022. Its totient is φ = 866642881020.

The previous prime is 866642881001. The next prime is 866642881057. The reversal of 866642881021 is 120188246668.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 862829200996 + 3813680025 = 928886^2 + 61755^2 .

It is a cyclic number.

It is not a de Polignac number, because 866642881021 - 2¹¹ = 866642878973 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 866642881021.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (866642881001) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 433321440510 + 433321440511.

It is an arithmetic number, because the mean of its divisors is an integer number (433321440511).

Almost surely, 2^866642881021 is an apocalyptic number.

It is an amenable number.

866642881021 is a deficient number, since it is larger than the sum of its proper divisors (1).

866642881021 is an equidigital number, since it uses as much as digits as its factorization.

866642881021 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 1769472, while the sum is 52.

The spelling of 866642881021 in words is "eight hundred sixty-six billion, six hundred forty-two million, eight hundred eighty-one thousand, twenty-one".