204861661 has 4 divisors (see below), whose sum is σ = 204925500. Its totient is φ = 204797824.

The previous prime is 204861659. The next prime is 204861691. The reversal of 204861661 is 166168402.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 166168402 = 2 ⋅83084201.

It can be written as a sum of positive squares in 2 ways, for example, as 118483225 + 86378436 = 10885^2 + 9294^2 .

It is a cyclic number.

It is not a de Polignac number, because 204861661 - 2¹ = 204861659 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (204861641) 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, 26836 + ... + 33613.

It is an arithmetic number, because the mean of its divisors is an integer number (51231375).

Almost surely, 2^204861661 is an apocalyptic number.

It is an amenable number.

204861661 is a deficient number, since it is larger than the sum of its proper divisors (63839).

204861661 is an equidigital number, since it uses as much as digits as its factorization.

204861661 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 63838.

The product of its (nonzero) digits is 13824, while the sum is 34.

The square root of 204861661 is about 14312.9892405465. The cubic root of 204861661 is about 589.5041903742.

The spelling of 204861661 in words is "two hundred four million, eight hundred sixty-one thousand, six hundred sixty-one".