204820561 has 4 divisors (see below), whose sum is σ = 223440624. Its totient is φ = 186200500.

The previous prime is 204820537. The next prime is 204820613. The reversal of 204820561 is 165028402.

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 204820561 - 2⁷ = 204820433 is a prime.

It is not an unprimeable number, because it can be changed into a prime (204820661) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 9310015 + ... + 9310036.

It is an arithmetic number, because the mean of its divisors is an integer number (55860156).

Almost surely, 2^204820561 is an apocalyptic number.

It is an amenable number.

204820561 is a deficient number, since it is larger than the sum of its proper divisors (18620063).

204820561 is a wasteful number, since it uses less digits than its factorization.

204820561 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 18620062.

The product of its (nonzero) digits is 3840, while the sum is 28.

The square root of 204820561 is about 14311.5534097456. The cubic root of 204820561 is about 589.4647650004.

Adding to 204820561 its reverse (165028402), we get a palindrome (369848963).

The spelling of 204820561 in words is "two hundred four million, eight hundred twenty thousand, five hundred sixty-one".