204020821 has 2 divisors, whose sum is σ = 204020822. Its totient is φ = 204020820.

The previous prime is 204020819. The next prime is 204020851. The reversal of 204020821 is 128020402.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 199656900 + 4363921 = 14130^2 + 2089^2 .

It is a cyclic number.

It is not a de Polignac number, because 204020821 - 2¹ = 204020819 is a prime.

Together with 204020819, it forms a pair of twin primes.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (204020851) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 102010410 + 102010411.

It is an arithmetic number, because the mean of its divisors is an integer number (102010411).

Almost surely, 2^204020821 is an apocalyptic number.

It is an amenable number.

204020821 is a deficient number, since it is larger than the sum of its proper divisors (1).

204020821 is an equidigital number, since it uses as much as digits as its factorization.

204020821 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 256, while the sum is 19.

The square root of 204020821 is about 14283.5857192793. The cubic root of 204020821 is about 588.6965585137.

The spelling of 204020821 in words is "two hundred four million, twenty thousand, eight hundred twenty-one".