81131894 has 16 divisors (see below), whose sum is σ = 124416000. Its totient is φ = 39669864.

The previous prime is 81131893. The next prime is 81131899. The reversal of 81131894 is 49813118.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81131893) 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, 14507 + ... + 19305.

It is an arithmetic number, because the mean of its divisors is an integer number (7776000).

Almost surely, 2^81131894 is an apocalyptic number.

81131894 is a deficient number, since it is larger than the sum of its proper divisors (43284106).

81131894 is a wasteful number, since it uses less digits than its factorization.

81131894 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4987.

The product of its digits is 6912, while the sum is 35.

The square root of 81131894 is about 9007.3244640126. The cubic root of 81131894 is about 432.9095882645.

The spelling of 81131894 in words is "eighty-one million, one hundred thirty-one thousand, eight hundred ninety-four".