204120021 has 16 divisors (see below), whose sum is σ = 327411200. Its totient is φ = 110500848.

The previous prime is 204120019. The next prime is 204120023. The reversal of 204120021 is 120021402.

It is an interprime number because it is at equal distance from previous prime (204120019) and next prime (204120023).

It is not a de Polignac number, because 204120021 - 2¹ = 204120019 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 204119979 and 204120006.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (204120023) 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, 255391 + ... + 256188.

It is an arithmetic number, because the mean of its divisors is an integer number (20463200).

Almost surely, 2^204120021 is an apocalyptic number.

204120021 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

It is an amenable number.

204120021 is a deficient number, since it is larger than the sum of its proper divisors (123291179).

204120021 is a wasteful number, since it uses less digits than its factorization.

204120021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 511608.

The product of its (nonzero) digits is 32, while the sum is 12.

The square root of 204120021 is about 14287.0578146797. The cubic root of 204120021 is about 588.7919560257.

Adding to 204120021 its reverse (120021402), we get a palindrome (324141423).

The spelling of 204120021 in words is "two hundred four million, one hundred twenty thousand, twenty-one".