81698 has 4 divisors (see below), whose sum is σ = 122550. Its totient is φ = 40848.

The previous prime is 81689. The next prime is 81701. The reversal of 81698 is 89618.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 89618 = 2 ⋅44809.

It can be written as a sum of positive squares in only one way, i.e., 64009 + 17689 = 253^2 + 133^2 .

It is an Ulam number.

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

It is an unprimeable number.

81698 is an untouchable number, because it is not equal to the sum of proper divisors of any number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 20423 + ... + 20426.

2⁸¹⁶⁹⁸ is an apocalyptic number.

81698 is a deficient number, since it is larger than the sum of its proper divisors (40852).

81698 is a wasteful number, since it uses less digits than its factorization.

81698 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 40851.

The product of its digits is 3456, while the sum is 32.

The square root of 81698 is about 285.8286199806. The cubic root of 81698 is about 43.3914145561.

The spelling of 81698 in words is "eighty-one thousand, six hundred ninety-eight".