81908 has 6 divisors (see below), whose sum is σ = 143346. Its totient is φ = 40952.

The previous prime is 81901. The next prime is 81919. The reversal of 81908 is 80918.

It can be written as a sum of positive squares in only one way, i.e., 77284 + 4624 = 278^2 + 68^2 .

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 81908.

It is not an unprimeable number, because it can be changed into a prime (81901) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10235 + ... + 10242.

It is an arithmetic number, because the mean of its divisors is an integer number (23891).

2⁸¹⁹⁰⁸ is an apocalyptic number.

It is an amenable number.

81908 is a deficient number, since it is larger than the sum of its proper divisors (61438).

81908 is a wasteful number, since it uses less digits than its factorization.

81908 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 20481 (or 20479 counting only the distinct ones).

The product of its (nonzero) digits is 576, while the sum is 26.

The square root of 81908 is about 286.1957372149. The cubic root of 81908 is about 43.4285611232.

Subtracting from 81908 its reverse (80918), we obtain a triangular number (990 = T₄₄).

It can be divided in two parts, 81 and 908, that added together give a palindrome (989).

The spelling of 81908 in words is "eighty-one thousand, nine hundred eight".