81639 has 12 divisors (see below), whose sum is σ = 121056. Its totient is φ = 52992.

The previous prime is 81637. The next prime is 81647. The reversal of 81639 is 93618.

81639 is nontrivially palindromic in base 12.

It is not a de Polignac number, because 81639 - 2¹ = 81637 is a prime.

It is a hoax number, since the sum of its digits (27) coincides with the sum of the digits of its distinct prime factors.

It is a congruent number.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 81639.

It is not an unprimeable number, because it can be changed into a prime (81637) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 327 + ... + 519.

It is an arithmetic number, because the mean of its divisors is an integer number (10088).

2⁸¹⁶³⁹ is an apocalyptic number.

81639 is a deficient number, since it is larger than the sum of its proper divisors (39417).

81639 is a wasteful number, since it uses less digits than its factorization.

81639 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 246 (or 243 counting only the distinct ones).

The product of its digits is 1296, while the sum is 27.

The square root of 81639 is about 285.7253926413. The cubic root of 81639 is about 43.3809666871.

The spelling of 81639 in words is "eighty-one thousand, six hundred thirty-nine".