181009 has 4 divisors (see below), whose sum is σ = 186880. Its totient is φ = 175140.

The previous prime is 181003. The next prime is 181019. The reversal of 181009 is 900181.

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, and also an emirpimes, since its reverse is a distinct semiprime: 900181 = 607 ⋅1483.

It is a cyclic number.

It is not a de Polignac number, because 181009 - 2³ = 181001 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (181001) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2889 + ... + 2950.

It is an arithmetic number, because the mean of its divisors is an integer number (46720).

2¹⁸¹⁰⁰⁹ is an apocalyptic number.

It is an amenable number.

181009 is a deficient number, since it is larger than the sum of its proper divisors (5871).

181009 is an equidigital number, since it uses as much as digits as its factorization.

181009 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5870.

The product of its (nonzero) digits is 72, while the sum is 19.

The square root of 181009 is about 425.4515248533. The cubic root of 181009 is about 56.5674658095.

The spelling of 181009 in words is "one hundred eighty-one thousand, nine".