206855909 has 4 divisors (see below), whose sum is σ = 222767916. Its totient is φ = 190943904.

The previous prime is 206855903. The next prime is 206855911. The reversal of 206855909 is 909558602.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 909558602 = 2 ⋅454779301.

It can be written as a sum of positive squares in 2 ways, for example, as 47541025 + 159314884 = 6895^2 + 12622^2 .

It is a cyclic number.

It is not a de Polignac number, because 206855909 - 2⁴ = 206855893 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 206855909.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (206855903) 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, 7955984 + ... + 7956009.

It is an arithmetic number, because the mean of its divisors is an integer number (55691979).

Almost surely, 2^206855909 is an apocalyptic number.

It is an amenable number.

206855909 is a deficient number, since it is larger than the sum of its proper divisors (15912007).

206855909 is a wasteful number, since it uses less digits than its factorization.

206855909 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 15912006.

The product of its (nonzero) digits is 194400, while the sum is 44.

The square root of 206855909 is about 14382.4861898074. The cubic root of 206855909 is about 591.4108808355.

The spelling of 206855909 in words is "two hundred six million, eight hundred fifty-five thousand, nine hundred nine".