81890 has 16 divisors (see below), whose sum is σ = 155520. Its totient is φ = 30960.

The previous prime is 81883. The next prime is 81899. The reversal of 81890 is 9818.

It is an alternating number because its digits alternate between even and odd.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (81899) by changing a digit.

81890 is an untouchable number, because it is not equal to the sum of proper divisors of any number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 26 + ... + 405.

It is an arithmetic number, because the mean of its divisors is an integer number (9720).

2⁸¹⁸⁹⁰ is an apocalyptic number.

81890 is a deficient number, since it is larger than the sum of its proper divisors (73630).

81890 is a wasteful number, since it uses less digits than its factorization.

81890 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 457.

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

The square root of 81890 is about 286.1642884778. The cubic root of 81890 is about 43.4253796213.

The spelling of 81890 in words is "eighty-one thousand, eight hundred ninety".