81998 has 8 divisors (see below), whose sum is σ = 140592. Its totient is φ = 35136.

The previous prime is 81973. The next prime is 82003. The reversal of 81998 is 89918.

It is a happy number.

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

It is a Curzon number.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2915 + ... + 2942.

It is an arithmetic number, because the mean of its divisors is an integer number (17574).

2⁸¹⁹⁹⁸ is an apocalyptic number.

81998 is a deficient number, since it is larger than the sum of its proper divisors (58594).

81998 is a wasteful number, since it uses less digits than its factorization.

81998 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5866.

The product of its digits is 5184, while the sum is 35.

The square root of 81998 is about 286.3529290928. The cubic root of 81998 is about 43.4444616449. Note that the first 4 decimals are identical.

The spelling of 81998 in words is "eighty-one thousand, nine hundred ninety-eight".