204220021 has 2 divisors, whose sum is σ = 204220022. Its totient is φ = 204220020.

The previous prime is 204220019. The next prime is 204220039. The reversal of 204220021 is 120022402.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 185340996 + 18879025 = 13614^2 + 4345^2 .

It is a cyclic number.

It is not a de Polignac number, because 204220021 - 2¹ = 204220019 is a prime.

Together with 204220019, it forms a pair of twin primes.

It is a junction number, because it is equal to n+sod(n) for n = 204219983 and 204220010.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (204220321) 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 as a sum of consecutive naturals, namely, 102110010 + 102110011.

It is an arithmetic number, because the mean of its divisors is an integer number (102110011).

Almost surely, 2^204220021 is an apocalyptic number.

It is an amenable number.

204220021 is a deficient number, since it is larger than the sum of its proper divisors (1).

204220021 is an equidigital number, since it uses as much as digits as its factorization.

204220021 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 64, while the sum is 13.

The square root of 204220021 is about 14290.5570570220. The cubic root of 204220021 is about 588.8880915947. Note that the first 3 decimals are identical.

Adding to 204220021 its reverse (120022402), we get a palindrome (324242423).

The spelling of 204220021 in words is "two hundred four million, two hundred twenty thousand, twenty-one".