204005561 has 16 divisors (see below), whose sum is σ = 216219648. Its totient is φ = 192099600.

The previous prime is 204005551. The next prime is 204005573. The reversal of 204005561 is 165500402.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-204005561 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (23).

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (204005551) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 616166 + ... + 616496.

It is an arithmetic number, because the mean of its divisors is an integer number (13513728).

Almost surely, 2^204005561 is an apocalyptic number.

It is an amenable number.

204005561 is a deficient number, since it is larger than the sum of its proper divisors (12214087).

204005561 is a wasteful number, since it uses less digits than its factorization.

204005561 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 692.

The product of its (nonzero) digits is 1200, while the sum is 23.

The square root of 204005561 is about 14283.0515296977. The cubic root of 204005561 is about 588.6818807087.

Adding to 204005561 its reverse (165500402), we get a palindrome (369505963).

The spelling of 204005561 in words is "two hundred four million, five thousand, five hundred sixty-one".