81131136 has 64 divisors (see below), whose sum is σ = 219218400. Its totient is φ = 26577920.

The previous prime is 81131129. The next prime is 81131137. The reversal of 81131136 is 63113118.

It is a tau number, because it is divible by the number of its divisors (64).

It is a super-2 number, since 2×81131136² = 13164522457300992, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (24).

It is a nude number because it is divisible by every one of its digits.

It is not an unprimeable number, because it can be changed into a prime (81131137) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 20866 + ... + 24446.

Almost surely, 2^81131136 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 81131136, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (109609200).

81131136 is an abundant number, since it is smaller than the sum of its proper divisors (138087264).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

81131136 is a wasteful number, since it uses less digits than its factorization.

81131136 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3657 (or 3645 counting only the distinct ones).

The product of its digits is 432, while the sum is 24.

The square root of 81131136 is about 9007.2823870466. The cubic root of 81131136 is about 432.9082400627.

The spelling of 81131136 in words is "eighty-one million, one hundred thirty-one thousand, one hundred thirty-six".