81139187 has 8 divisors (see below), whose sum is σ = 86206800. Its totient is φ = 76222944.

The previous prime is 81139171. The next prime is 81139199. The reversal of 81139187 is 78193118.

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

It is a cyclic number.

It is not a de Polignac number, because 81139187 - 2⁴ = 81139171 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 81139187.

It is not an unprimeable number, because it can be changed into a prime (81130187) 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, 36737 + ... + 38882.

It is an arithmetic number, because the mean of its divisors is an integer number (10775850).

Almost surely, 2^81139187 is an apocalyptic number.

81139187 is a deficient number, since it is larger than the sum of its proper divisors (5067613).

81139187 is a wasteful number, since it uses less digits than its factorization.

81139187 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 75685.

The product of its digits is 12096, while the sum is 38.

The square root of 81139187 is about 9007.7292921135. The cubic root of 81139187 is about 432.9225593862.

The spelling of 81139187 in words is "eighty-one million, one hundred thirty-nine thousand, one hundred eighty-seven".