204000021 has 24 divisors (see below), whose sum is σ = 303390360. Its totient is φ = 132028416.

The previous prime is 204000011. The next prime is 204000023. The reversal of 204000021 is 120000402.

It can be written as a sum of positive squares in 4 ways, for example, as 10400625 + 193599396 = 3225^2 + 13914^2 .

It is not a de Polignac number, because 204000021 - 2⁵ = 203999989 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (9).

It is a junction number, because it is equal to n+sod(n) for n = 203999967 and 204000012.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (204000023) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 44065 + ... + 48473.

It is an arithmetic number, because the mean of its divisors is an integer number (12641265).

Almost surely, 2^204000021 is an apocalyptic number.

It is an amenable number.

204000021 is a deficient number, since it is larger than the sum of its proper divisors (99390339).

204000021 is a wasteful number, since it uses less digits than its factorization.

204000021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4565 (or 4562 counting only the distinct ones).

The product of its (nonzero) digits is 16, while the sum is 9.

The square root of 204000021 is about 14282.8575922327. The cubic root of 204000021 is about 588.6765518880.

Adding to 204000021 its reverse (120000402), we get a palindrome (324000423).

The spelling of 204000021 in words is "two hundred four million, twenty-one", and thus it is an aban number.