205989477909 has 4 divisors (see below), whose sum is σ = 274652637216. Its totient is φ = 137326318604.

The previous prime is 205989477901. The next prime is 205989477943. The reversal of 205989477909 is 909774989502.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 205989477909 - 2³ = 205989477901 is a prime.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (205989477901) 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, 34331579649 + ... + 34331579654.

It is an arithmetic number, because the mean of its divisors is an integer number (68663159304).

Almost surely, 2^205989477909 is an apocalyptic number.

It is an amenable number.

205989477909 is a deficient number, since it is larger than the sum of its proper divisors (68663159307).

205989477909 is an equidigital number, since it uses as much as digits as its factorization.

205989477909 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 68663159306.

The product of its (nonzero) digits is 102876480, while the sum is 69.

The spelling of 205989477909 in words is "two hundred five billion, nine hundred eighty-nine million, four hundred seventy-seven thousand, nine hundred nine".