81839139 has 16 divisors (see below), whose sum is σ = 115936128. Its totient is φ = 51172992.

The previous prime is 81839123. The next prime is 81839159. The reversal of 81839139 is 93193818.

It is a happy number.

It is not a de Polignac number, because 81839139 - 2⁴ = 81839123 is a prime.

It is a super-2 number, since 2×81839139² = 13395289344522642, which contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 81839139.

It is not an unprimeable number, because it can be changed into a prime (81839159) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 13044 + ... + 18270.

It is an arithmetic number, because the mean of its divisors is an integer number (7246008).

Almost surely, 2^81839139 is an apocalyptic number.

81839139 is a deficient number, since it is larger than the sum of its proper divisors (34096989).

81839139 is a wasteful number, since it uses less digits than its factorization.

81839139 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5554.

The product of its digits is 46656, while the sum is 42.

The square root of 81839139 is about 9046.4987149726. The cubic root of 81839139 is about 434.1638741368.

The spelling of 81839139 in words is "eighty-one million, eight hundred thirty-nine thousand, one hundred thirty-nine".