181861 has 4 divisors (see below), whose sum is σ = 189792. Its totient is φ = 173932.

The previous prime is 181837. The next prime is 181871. The reversal of 181861 is 168181.

It is a happy number.

181861 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, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 181861 - 2¹¹ = 179813 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (181871) 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, 3931 + ... + 3976.

It is an arithmetic number, because the mean of its divisors is an integer number (47448).

2¹⁸¹⁸⁶¹ is an apocalyptic number.

It is an amenable number.

181861 is a deficient number, since it is larger than the sum of its proper divisors (7931).

181861 is an equidigital number, since it uses as much as digits as its factorization.

181861 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7930.

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

The square root of 181861 is about 426.4516385242. The cubic root of 181861 is about 56.6560802984.

The spelling of 181861 in words is "one hundred eighty-one thousand, eight hundred sixty-one".