204661661 has 4 divisors (see below), whose sum is σ = 204690300. Its totient is φ = 204633024.

The previous prime is 204661621. The next prime is 204661669. The reversal of 204661661 is 166166402.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length, and also an emirpimes, since its reverse is a distinct semiprime: 166166402 = 2 ⋅83083201.

It can be written as a sum of positive squares in 2 ways, for example, as 176730436 + 27931225 = 13294^2 + 5285^2 .

It is a cyclic number.

It is not a de Polignac number, because 204661661 - 2¹⁴ = 204645277 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (204661669) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 6245 + ... + 21173.

It is an arithmetic number, because the mean of its divisors is an integer number (51172575).

Almost surely, 2^204661661 is an apocalyptic number.

It is an amenable number.

204661661 is a deficient number, since it is larger than the sum of its proper divisors (28639).

204661661 is a wasteful number, since it uses less digits than its factorization.

204661661 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 28638.

The product of its (nonzero) digits is 10368, while the sum is 32.

The square root of 204661661 is about 14306.0008737592. Note that the first 3 decimals coincide. The cubic root of 204661661 is about 589.3122897749.

The spelling of 204661661 in words is "two hundred four million, six hundred sixty-one thousand, six hundred sixty-one".