172809 has 24 divisors (see below), whose sum is σ = 308672. Its totient is φ = 90720.

The previous prime is 172807. The next prime is 172829. The reversal of 172809 is 908271.

It is not a de Polignac number, because 172809 - 2¹ = 172807 is a prime.

It is an Ulam number.

172809 is a lucky number.

It is not an unprimeable number, because it can be changed into a prime (172801) 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 23 ways as a sum of consecutive naturals, for example, 714 + ... + 924.

2¹⁷²⁸⁰⁹ is an apocalyptic number.

It is an amenable number.

172809 is a deficient number, since it is larger than the sum of its proper divisors (135863).

172809 is a wasteful number, since it uses less digits than its factorization.

172809 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 237 (or 234 counting only the distinct ones).

The product of its (nonzero) digits is 1008, while the sum is 27.

The square root of 172809 is about 415.7030189931. The cubic root of 172809 is about 55.7000329842.

The spelling of 172809 in words is "one hundred seventy-two thousand, eight hundred nine".