205640613 has 10 divisors (see below), whose sum is σ = 307191654. Its totient is φ = 137093688.

The previous prime is 205640609. The next prime is 205640623. The reversal of 205640613 is 316046502.

205640613 is a `hidden beast` number, since 2 + 0 + 5 + 6 + 40 + 613 = 666.

It can be written as a sum of positive squares in only one way, i.e., 154703844 + 50936769 = 12438^2 + 7137^2 .

It is not a de Polignac number, because 205640613 - 2² = 205640609 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (205640623) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 9 ways as a sum of consecutive naturals, for example, 1269306 + ... + 1269467.

Almost surely, 2^205640613 is an apocalyptic number.

It is an amenable number.

205640613 is a deficient number, since it is larger than the sum of its proper divisors (101551041).

205640613 is an equidigital number, since it uses as much as digits as its factorization.

205640613 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2538785 (or 2538776 counting only the distinct ones).

The product of its (nonzero) digits is 4320, while the sum is 27.

The square root of 205640613 is about 14340.1747897297. The cubic root of 205640613 is about 590.2504088836.

The spelling of 205640613 in words is "two hundred five million, six hundred forty thousand, six hundred thirteen".