206991309 has 16 divisors (see below), whose sum is σ = 325591040. Its totient is φ = 114464880.

The previous prime is 206991289. The next prime is 206991311. The reversal of 206991309 is 903199602.

It is a happy number.

It is not a de Polignac number, because 206991309 - 2⁵ = 206991277 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (206991359) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 158329 + ... + 159630.

It is an arithmetic number, because the mean of its divisors is an integer number (20349440).

Almost surely, 2^206991309 is an apocalyptic number.

It is an amenable number.

206991309 is a deficient number, since it is larger than the sum of its proper divisors (118599731).

206991309 is a wasteful number, since it uses less digits than its factorization.

206991309 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 318000.

The product of its (nonzero) digits is 26244, while the sum is 39.

The square root of 206991309 is about 14387.1925336391. The cubic root of 206991309 is about 591.5398910375.

The spelling of 206991309 in words is "two hundred six million, nine hundred ninety-one thousand, three hundred nine".