81131185689 has 4 divisors (see below), whose sum is σ = 108174914256. Its totient is φ = 54087457124.

The previous prime is 81131185669. The next prime is 81131185691. The reversal of 81131185689 is 98658113118.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 81131185689 - 2⁷ = 81131185561 is a prime.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (81131185649) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 13521864279 + ... + 13521864284.

It is an arithmetic number, because the mean of its divisors is an integer number (27043728564).

Almost surely, 2^81131185689 is an apocalyptic number.

It is an amenable number.

81131185689 is a deficient number, since it is larger than the sum of its proper divisors (27043728567).

81131185689 is a wasteful number, since it uses less digits than its factorization.

81131185689 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 27043728566.

The product of its digits is 414720, while the sum is 51.

The spelling of 81131185689 in words is "eighty-one billion, one hundred thirty-one million, one hundred eighty-five thousand, six hundred eighty-nine".