81689 has 2 divisors, whose sum is σ = 81690. Its totient is φ = 81688.

The previous prime is 81677. The next prime is 81701. The reversal of 81689 is 98618.

It is a balanced prime because it is at equal distance from previous prime (81677) and next prime (81701).

It can be written as a sum of positive squares in only one way, i.e., 80089 + 1600 = 283^2 + 40^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-81689 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (81619) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40844 + 40845.

It is an arithmetic number, because the mean of its divisors is an integer number (40845).

2⁸¹⁶⁸⁹ is an apocalyptic number.

It is an amenable number.

81689 is a deficient number, since it is larger than the sum of its proper divisors (1).

81689 is an equidigital number, since it uses as much as digits as its factorization.

81689 is an evil number, because the sum of its binary digits is even.

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

The square root of 81689 is about 285.8128758471. The cubic root of 81689 is about 43.3898211385.

The spelling of 81689 in words is "eighty-one thousand, six hundred eighty-nine".