205689924661 has 64 divisors (see below), whose sum is σ = 245917425600. Its totient is φ = 170272751616.

The previous prime is 205689924659. The next prime is 205689924677. The reversal of 205689924661 is 166429986502.

205689924661 = 320694² + 320695².

205689924661 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It can be written as a sum of positive squares in 32 ways, for example, as 69008137636 + 136681787025 = 262694^2 + 369705^2 .

It is a 10-Lehmer number, since φ(205689924661) divides (205689924661-1)¹⁰.

It is a cyclic number.

It is not a de Polignac number, because 205689924661 - 2¹ = 205689924659 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 205689924596 and 205689924605.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (205689924161) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 79323781 + ... + 79326373.

It is an arithmetic number, because the mean of its divisors is an integer number (3842459775).

Almost surely, 2^205689924661 is an apocalyptic number.

205689924661 is the 320695-th centered square number.

It is an amenable number.

205689924661 is a deficient number, since it is larger than the sum of its proper divisors (40227500939).

205689924661 is a wasteful number, since it uses less digits than its factorization.

205689924661 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2858.

The product of its (nonzero) digits is 11197440, while the sum is 58.

The spelling of 205689924661 in words is "two hundred five billion, six hundred eighty-nine million, nine hundred twenty-four thousand, six hundred sixty-one".