81911558 has 8 divisors (see below), whose sum is σ = 123692400. Its totient is φ = 40680760.

The previous prime is 81911551. The next prime is 81911561. The reversal of 81911558 is 85511918.

It is a happy number.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81911551) 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, 137138 + ... + 137733.

It is an arithmetic number, because the mean of its divisors is an integer number (15461550).

Almost surely, 2^81911558 is an apocalyptic number.

81911558 is a deficient number, since it is larger than the sum of its proper divisors (41780842).

81911558 is a wasteful number, since it uses less digits than its factorization.

81911558 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 275022.

The product of its digits is 14400, while the sum is 38.

The square root of 81911558 is about 9050.5004281531. The cubic root of 81911558 is about 434.2918994490.

The spelling of 81911558 in words is "eighty-one million, nine hundred eleven thousand, five hundred fifty-eight".