81581911 has 8 divisors (see below), whose sum is σ = 82905984. Its totient is φ = 80262840.

The previous prime is 81581909. The next prime is 81581917. The reversal of 81581911 is 11918518.

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

It is a cyclic number.

It is not a de Polignac number, because 81581911 - 2¹ = 81581909 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 (81581917) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 44760 + ... + 46546.

It is an arithmetic number, because the mean of its divisors is an integer number (10363248).

Almost surely, 2^81581911 is an apocalyptic number.

81581911 is a deficient number, since it is larger than the sum of its proper divisors (1324073).

81581911 is a wasteful number, since it uses less digits than its factorization.

81581911 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2501.

The product of its digits is 2880, while the sum is 34.

The square root of 81581911 is about 9032.2705340352. The cubic root of 81581911 is about 433.7085243003.

The spelling of 81581911 in words is "eighty-one million, five hundred eighty-one thousand, nine hundred eleven".