81131911 has 8 divisors (see below), whose sum is σ = 92912000. Its totient is φ = 69399288.

The previous prime is 81131899. The next prime is 81131933. The reversal of 81131911 is 11913118.

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

It is not a de Polignac number, because 81131911 - 2¹⁵ = 81099143 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 (81132911) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 8121 + ... + 15106.

It is an arithmetic number, because the mean of its divisors is an integer number (11614000).

Almost surely, 2^81131911 is an apocalyptic number.

81131911 is a deficient number, since it is larger than the sum of its proper divisors (11780089).

81131911 is a wasteful number, since it uses less digits than its factorization.

81131911 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 23733.

The product of its digits is 216, while the sum is 25.

The square root of 81131911 is about 9007.3254076890. The cubic root of 81131911 is about 432.9096185011.

The spelling of 81131911 in words is "eighty-one million, one hundred thirty-one thousand, nine hundred eleven".