81558249191 has 4 divisors (see below), whose sum is σ = 82058606712. Its totient is φ = 81057891672.

The previous prime is 81558249187. The next prime is 81558249203. The reversal of 81558249191 is 19194285518.

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 81558249191 - 2² = 81558249187 is a prime.

It is a super-2 number, since 2×81558249191² (a number of 23 digits) contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81558249691) 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, 250178516 + ... + 250178841.

It is an arithmetic number, because the mean of its divisors is an integer number (20514651678).

Almost surely, 2^81558249191 is an apocalyptic number.

81558249191 is a deficient number, since it is larger than the sum of its proper divisors (500357521).

81558249191 is a wasteful number, since it uses less digits than its factorization.

81558249191 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 500357520.

The product of its digits is 1036800, while the sum is 53.

The spelling of 81558249191 in words is "eighty-one billion, five hundred fifty-eight million, two hundred forty-nine thousand, one hundred ninety-one".