811959835921 has 4 divisors (see below), whose sum is σ = 874418284852. Its totient is φ = 749501386992.

The previous prime is 811959835787. The next prime is 811959835987. The reversal of 811959835921 is 129538959118.

811959835921 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 129538959118 = 2 ⋅64769479559.

It can be written as a sum of positive squares in 2 ways, for example, as 368351886400 + 443607949521 = 606920^2 + 666039^2 .

It is a cyclic number.

It is not a de Polignac number, because 811959835921 - 2¹⁵ = 811959803153 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 811959835921.

It is not an unprimeable number, because it can be changed into a prime (811959835721) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 31229224446 + ... + 31229224471.

It is an arithmetic number, because the mean of its divisors is an integer number (218604571213).

Almost surely, 2^811959835921 is an apocalyptic number.

It is an amenable number.

811959835921 is a deficient number, since it is larger than the sum of its proper divisors (62458448931).

811959835921 is a wasteful number, since it uses less digits than its factorization.

811959835921 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 62458448930.

The product of its digits is 6998400, while the sum is 61.

The spelling of 811959835921 in words is "eight hundred eleven billion, nine hundred fifty-nine million, eight hundred thirty-five thousand, nine hundred twenty-one".