81108673955821 has 4 divisors (see below), whose sum is σ = 81120828716572. Its totient is φ = 81096519195072.

The previous prime is 81108673955819. The next prime is 81108673955873. The reversal of 81108673955821 is 12855937680118.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 1859704964100 + 79248968991721 = 1363710^2 + 8902189^2 .

It is a cyclic number.

It is not a de Polignac number, because 81108673955821 - 2¹ = 81108673955819 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81108673953821) 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, 6077370366 + ... + 6077383711.

It is an arithmetic number, because the mean of its divisors is an integer number (20280207179143).

Almost surely, 2^{81108673955821} is an apocalyptic number.

It is an amenable number.

81108673955821 is a deficient number, since it is larger than the sum of its proper divisors (12154760751).

81108673955821 is a wasteful number, since it uses less digits than its factorization.

81108673955821 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 12154760750.

The product of its (nonzero) digits is 29030400, while the sum is 64.

The spelling of 81108673955821 in words is "eighty-one trillion, one hundred eight billion, six hundred seventy-three million, nine hundred fifty-five thousand, eight hundred twenty-one".