204821 has 2 divisors, whose sum is σ = 204822. Its totient is φ = 204820.

The previous prime is 204803. The next prime is 204857. The reversal of 204821 is 128402.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 192721 + 12100 = 439^2 + 110^2 .

It is a cyclic number.

It is not a de Polignac number, because 204821 - 2¹⁴ = 188437 is a prime.

It is a Chen prime.

It is a self number, because there is not a number n which added to its sum of digits gives 204821.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (204871) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 102410 + 102411.

It is an arithmetic number, because the mean of its divisors is an integer number (102411).

2²⁰⁴⁸²¹ is an apocalyptic number.

It is an amenable number.

204821 is a deficient number, since it is larger than the sum of its proper divisors (1).

204821 is an equidigital number, since it uses as much as digits as its factorization.

204821 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 128, while the sum is 17.

The square root of 204821 is about 452.5715413059. The cubic root of 204821 is about 58.9465186141.

The spelling of 204821 in words is "two hundred four thousand, eight hundred twenty-one".