181681 has 4 divisors (see below), whose sum is σ = 183652. Its totient is φ = 179712.

The previous prime is 181669. The next prime is 181693. The reversal of 181681 is 186181.

It is a happy number.

181681 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

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

It is an interprime number because it is at equal distance from previous prime (181669) and next prime (181693).

It can be written as a sum of positive squares in 2 ways, for example, as 34225 + 147456 = 185^2 + 384^2 .

It is a cyclic number.

It is not a de Polignac number, because 181681 - 2⁷ = 181553 is a prime.

It is a super-2 number, since 2×181681² = 66015971522, which contains 22 as substring.

It is a Duffinian number.

It is a plaindrome in base 11.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (181081) 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, 840 + ... + 1033.

It is an arithmetic number, because the mean of its divisors is an integer number (45913).

2¹⁸¹⁶⁸¹ is an apocalyptic number.

It is an amenable number.

181681 is a deficient number, since it is larger than the sum of its proper divisors (1971).

181681 is an equidigital number, since it uses as much as digits as its factorization.

181681 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1970.

The product of its digits is 384, while the sum is 25.

The square root of 181681 is about 426.2405424171. The cubic root of 181681 is about 56.6373820236.

The spelling of 181681 in words is "one hundred eighty-one thousand, six hundred eighty-one".