205817985 has 12 divisors (see below), whose sum is σ = 356751252. Its totient is φ = 109769568.

The previous prime is 205817951. The next prime is 205817993. The reversal of 205817985 is 589718502.

It is a happy number.

It can be written as a sum of positive squares in 2 ways, for example, as 26873856 + 178944129 = 5184^2 + 13377^2 .

It is not a de Polignac number, because 205817985 - 2⁹ = 205817473 is a prime.

It is a super-2 number, since 2×205817985² = 84722085898920450, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (45), and also a Moran number because the ratio is a prime number: 4573733 = 205817985 / (2 + 0 + 5 + 8 + 1 + 7 + 9 + 8 + 5).

It is a self number, because there is not a number n which added to its sum of digits gives 205817985.

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 2286822 + ... + 2286911.

It is an arithmetic number, because the mean of its divisors is an integer number (29729271).

Almost surely, 2^205817985 is an apocalyptic number.

It is an amenable number.

205817985 is a deficient number, since it is larger than the sum of its proper divisors (150933267).

205817985 is a wasteful number, since it uses less digits than its factorization.

205817985 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4573744 (or 4573741 counting only the distinct ones).

The product of its (nonzero) digits is 201600, while the sum is 45.

The square root of 205817985 is about 14346.3579001780. The cubic root of 205817985 is about 590.4200637777.

The spelling of 205817985 in words is "two hundred five million, eight hundred seventeen thousand, nine hundred eighty-five".