166189909 has 4 divisors (see below), whose sum is σ = 175965804. Its totient is φ = 156414016.

The previous prime is 166189879. The next prime is 166189921. The reversal of 166189909 is 909981661.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 909981661 = 17 ⋅53528333.

It can be written as a sum of positive squares in 2 ways, for example, as 112826884 + 53363025 = 10622^2 + 7305^2 .

It is a cyclic number.

It is not a de Polignac number, because 166189909 - 2¹⁵ = 166157141 is a prime.

It is a super-3 number, since 3×166189909³ (a number of 26 digits) contains 333 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (166189999) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 4887922 + ... + 4887955.

It is an arithmetic number, because the mean of its divisors is an integer number (43991451).

Almost surely, 2^166189909 is an apocalyptic number.

It is an amenable number.

166189909 is a deficient number, since it is larger than the sum of its proper divisors (9775895).

166189909 is an equidigital number, since it uses as much as digits as its factorization.

166189909 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9775894.

The product of its (nonzero) digits is 209952, while the sum is 49.

The square root of 166189909 is about 12891.4665185928. The cubic root of 166189909 is about 549.7959672948.

The spelling of 166189909 in words is "one hundred sixty-six million, one hundred eighty-nine thousand, nine hundred nine".