81191868431 has 4 divisors (see below), whose sum is σ = 81197709672. Its totient is φ = 81186027192.

The previous prime is 81191868409. The next prime is 81191868473. The reversal of 81191868431 is 13486819118.

It is a happy number.

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

It is a cyclic number.

It is not a de Polignac number, because 81191868431 - 2¹⁴ = 81191852047 is a prime.

It is a super-2 number, since 2×81191868431² (a number of 23 digits) contains 22 as substring.

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 81191868431.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81191861431) 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, 2899721 + ... + 2927586.

It is an arithmetic number, because the mean of its divisors is an integer number (20299427418).

Almost surely, 2^81191868431 is an apocalyptic number.

81191868431 is a deficient number, since it is larger than the sum of its proper divisors (5841241).

81191868431 is a wasteful number, since it uses less digits than its factorization.

81191868431 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5841240.

The product of its digits is 331776, while the sum is 50.

The spelling of 81191868431 in words is "eighty-one billion, one hundred ninety-one million, eight hundred sixty-eight thousand, four hundred thirty-one".