81139189 has 4 divisors (see below), whose sum is σ = 81194400. Its totient is φ = 81083980.

The previous prime is 81139171. The next prime is 81139199. The reversal of 81139189 is 98193118.

It is a happy number.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 81139189 - 2²¹ = 79042037 is a prime.

It is a Smith number, since the sum of its digits (40) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81139109) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 25339 + ... + 28360.

It is an arithmetic number, because the mean of its divisors is an integer number (20298600).

Almost surely, 2^81139189 is an apocalyptic number.

It is an amenable number.

81139189 is a deficient number, since it is larger than the sum of its proper divisors (55211).

81139189 is a wasteful number, since it uses less digits than its factorization.

81139189 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 55210.

The product of its digits is 15552, while the sum is 40.

The square root of 81139189 is about 9007.7294031293. The cubic root of 81139189 is about 432.9225629433.

It can be divided in two parts, 811 and 39189, that added together give a square (40000 = 200²).

The spelling of 81139189 in words is "eighty-one million, one hundred thirty-nine thousand, one hundred eighty-nine".