205688681 has 4 divisors (see below), whose sum is σ = 224387664. Its totient is φ = 186989700.

The previous prime is 205688671. The next prime is 205688687. The reversal of 205688681 is 186886502.

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 205688681 - 2⁶ = 205688617 is a prime.

It is a super-2 number, since 2×205688681² = 84615666983039522, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (205688687) 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 3 ways as a sum of consecutive naturals, for example, 9349475 + ... + 9349496.

It is an arithmetic number, because the mean of its divisors is an integer number (56096916).

Almost surely, 2^205688681 is an apocalyptic number.

It is an amenable number.

205688681 is a deficient number, since it is larger than the sum of its proper divisors (18698983).

205688681 is a wasteful number, since it uses less digits than its factorization.

205688681 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 18698982.

The product of its (nonzero) digits is 184320, while the sum is 44.

The square root of 205688681 is about 14341.8506825305. The cubic root of 205688681 is about 590.2963951731.

It can be divided in two parts, 205 and 688681, that added together give a palindrome (688886).

The spelling of 205688681 in words is "two hundred five million, six hundred eighty-eight thousand, six hundred eighty-one".