205509317 has 4 divisors (see below), whose sum is σ = 221317740. Its totient is φ = 189700896.

The previous prime is 205509253. The next prime is 205509319. The reversal of 205509317 is 713905502.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 82609921 + 122899396 = 9089^2 + 11086^2 .

It is a cyclic number.

It is not a de Polignac number, because 205509317 - 2⁶ = 205509253 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 (205509319) 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, 7904192 + ... + 7904217.

It is an arithmetic number, because the mean of its divisors is an integer number (55329435).

Almost surely, 2^205509317 is an apocalyptic number.

It is an amenable number.

205509317 is a deficient number, since it is larger than the sum of its proper divisors (15808423).

205509317 is a wasteful number, since it uses less digits than its factorization.

205509317 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 15808422.

The product of its (nonzero) digits is 9450, while the sum is 32.

The square root of 205509317 is about 14335.5961508407. The cubic root of 205509317 is about 590.1247624694.

The spelling of 205509317 in words is "two hundred five million, five hundred nine thousand, three hundred seventeen".