81609 has 8 divisors (see below), whose sum is σ = 118752. Its totient is φ = 49440.

The previous prime is 81569. The next prime is 81611. The reversal of 81609 is 90618.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 81609 - 2⁸ = 81353 is a prime.

81609 is a lucky number.

It is not an unprimeable number, because it can be changed into a prime (81619) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1204 + ... + 1269.

It is an arithmetic number, because the mean of its divisors is an integer number (14844).

2⁸¹⁶⁰⁹ is an apocalyptic number.

It is an amenable number.

81609 is a deficient number, since it is larger than the sum of its proper divisors (37143).

81609 is a wasteful number, since it uses less digits than its factorization.

81609 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2487.

The product of its (nonzero) digits is 432, while the sum is 24.

The square root of 81609 is about 285.6728898583. The cubic root of 81609 is about 43.3756522809.

Subtracting 81609 from its reverse (90618), we obtain a palindrome (9009).

The spelling of 81609 in words is "eighty-one thousand, six hundred nine".