172189309 has 4 divisors (see below), whose sum is σ = 172499004. Its totient is φ = 171879616.

The previous prime is 172189291. The next prime is 172189319. The reversal of 172189309 is 903981271.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 903981271 = 18287 ⋅49433.

It can be written as a sum of positive squares in 2 ways, for example, as 111302500 + 60886809 = 10550^2 + 7803^2 .

It is a 3-Lehmer number, since φ(172189309) divides (172189309-1)³.

It is a cyclic number.

It is not a de Polignac number, because 172189309 - 2⁷ = 172189181 is a prime.

It is a Smith number, since the sum of its digits (40) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (172189319) by changing a digit.

It is a nontrivial repunit in base 556.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 154012 + ... + 155125.

It is an arithmetic number, because the mean of its divisors is an integer number (43124751).

Almost surely, 2^172189309 is an apocalyptic number.

It is an amenable number.

172189309 is a deficient number, since it is larger than the sum of its proper divisors (309695).

172189309 is an equidigital number, since it uses as much as digits as its factorization.

172189309 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 309694.

The product of its (nonzero) digits is 27216, while the sum is 40.

The square root of 172189309 is about 13122.0924017475. The cubic root of 172189309 is about 556.3337335716. Note that the first 3 decimals are identical.

The spelling of 172189309 in words is "one hundred seventy-two million, one hundred eighty-nine thousand, three hundred nine".