81138189 has 32 divisors (see below), whose sum is σ = 125199360. Its totient is φ = 46224000.

The previous prime is 81138179. The next prime is 81138223. The reversal of 81138189 is 98183118.

It is not a de Polignac number, because 81138189 - 2¹² = 81134093 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81138149) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 94249 + ... + 95105.

It is an arithmetic number, because the mean of its divisors is an integer number (3912480).

Almost surely, 2^81138189 is an apocalyptic number.

It is an amenable number.

81138189 is a deficient number, since it is larger than the sum of its proper divisors (44061171).

81138189 is a wasteful number, since it uses less digits than its factorization.

81138189 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1041.

The product of its digits is 13824, while the sum is 39.

The square root of 81138189 is about 9007.6738950741. The cubic root of 81138189 is about 432.9207844178.

The spelling of 81138189 in words is "eighty-one million, one hundred thirty-eight thousand, one hundred eighty-nine".