204221021 has 4 divisors (see below), whose sum is σ = 204537312. Its totient is φ = 203904732.

The previous prime is 204220999. The next prime is 204221029. The reversal of 204221021 is 120122402.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also an emirpimes, since its reverse is a distinct semiprime: 120122402 = 2 ⋅60061201.

It is a cyclic number.

It is not a de Polignac number, because 204221021 - 2⁶ = 204220957 is a prime.

It is a super-3 number, since 3×204221021³ (a number of 26 digits) contains 333 as substring.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 204220987 and 204221005.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (204221029) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 157175 + ... + 158468.

It is an arithmetic number, because the mean of its divisors is an integer number (51134328).

Almost surely, 2^204221021 is an apocalyptic number.

It is an amenable number.

204221021 is a deficient number, since it is larger than the sum of its proper divisors (316291).

204221021 is an equidigital number, since it uses as much as digits as its factorization.

204221021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 316290.

The product of its (nonzero) digits is 64, while the sum is 14.

The square root of 204221021 is about 14290.5920451184. The cubic root of 204221021 is about 588.8890527919.

Adding to 204221021 its reverse (120122402), we get a palindrome (324343423).

The spelling of 204221021 in words is "two hundred four million, two hundred twenty-one thousand, twenty-one".