181609 has 2 divisors, whose sum is σ = 181610. Its totient is φ = 181608.

The previous prime is 181607. The next prime is 181619. The reversal of 181609 is 906181.

181609 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 160000 + 21609 = 400^2 + 147^2 .

It is a cyclic number.

It is not a de Polignac number, because 181609 - 2¹ = 181607 is a prime.

Together with 181607, it forms a pair of twin primes.

It is equal to p₁₆₄₅₉ and since 181609 and 16459 have the same sum of digits, it is a Honaker prime.

It is a plaindrome in base 11.

It is not a weakly prime, because it can be changed into another prime (181603) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 90804 + 90805.

It is an arithmetic number, because the mean of its divisors is an integer number (90805).

2¹⁸¹⁶⁰⁹ is an apocalyptic number.

It is an amenable number.

181609 is a deficient number, since it is larger than the sum of its proper divisors (1).

181609 is an equidigital number, since it uses as much as digits as its factorization.

181609 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 432, while the sum is 25.

The square root of 181609 is about 426.1560746956. The cubic root of 181609 is about 56.6298992556.

The spelling of 181609 in words is "one hundred eighty-one thousand, six hundred nine".