81705 has 16 divisors (see below), whose sum is σ = 141120. Its totient is φ = 40128.

The previous prime is 81703. The next prime is 81707. The reversal of 81705 is 50718.

81705 = T₁₄ + T₁₅ + ... + T₇₈.

It is a happy number.

It is an interprime number because it is at equal distance from previous prime (81703) and next prime (81707).

It is not a de Polignac number, because 81705 - 2¹ = 81703 is a prime.

It is a Curzon number.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 81705.

It is not an unprimeable number, because it can be changed into a prime (81701) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 15 + ... + 404.

It is an arithmetic number, because the mean of its divisors is an integer number (8820).

2⁸¹⁷⁰⁵ is an apocalyptic number.

It is an amenable number.

81705 is a deficient number, since it is larger than the sum of its proper divisors (59415).

81705 is a wasteful number, since it uses less digits than its factorization.

81705 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 440.

The product of its (nonzero) digits is 280, while the sum is 21.

The square root of 81705 is about 285.8408648182. The cubic root of 81705 is about 43.3926537999.

The spelling of 81705 in words is "eighty-one thousand, seven hundred five".