81745 has 4 divisors (see below), whose sum is σ = 98100. Its totient is φ = 65392.

The previous prime is 81737. The next prime is 81749. The reversal of 81745 is 54718.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 20736 + 61009 = 144^2 + 247^2 .

It is a cyclic number.

It is not a de Polignac number, because 81745 - 2³ = 81737 is a prime.

81745 is a lucky number.

It is not an unprimeable number, because it can be changed into a prime (81749) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 8170 + ... + 8179.

It is an arithmetic number, because the mean of its divisors is an integer number (24525).

2⁸¹⁷⁴⁵ is an apocalyptic number.

It is an amenable number.

81745 is a deficient number, since it is larger than the sum of its proper divisors (16355).

81745 is a wasteful number, since it uses less digits than its factorization.

81745 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 16354.

The product of its digits is 1120, while the sum is 25.

The square root of 81745 is about 285.9108252585. The cubic root of 81745 is about 43.3997338357.

The spelling of 81745 in words is "eighty-one thousand, seven hundred forty-five".