191808009 has 6 divisors (see below), whose sum is σ = 277056026. Its totient is φ = 127872000.

The previous prime is 191807981. The next prime is 191808013. The reversal of 191808009 is 900808191.

It can be written as a sum of positive squares in only one way, i.e., 130028409 + 61779600 = 11403^2 + 7860^2 .

It is not a de Polignac number, because 191808009 - 2⁵ = 191807977 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (191808049) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 10655992 + ... + 10656009.

Almost surely, 2^191808009 is an apocalyptic number.

It is an amenable number.

191808009 is a deficient number, since it is larger than the sum of its proper divisors (85248017).

191808009 is a wasteful number, since it uses less digits than its factorization.

191808009 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 21312007 (or 21312004 counting only the distinct ones).

The product of its (nonzero) digits is 5184, while the sum is 36.

The square root of 191808009 is about 13849.4768493254. The cubic root of 191808009 is about 576.7074730647.

The spelling of 191808009 in words is "one hundred ninety-one million, eight hundred eight thousand, nine".