204191021 has 2 divisors, whose sum is σ = 204191022. Its totient is φ = 204191020.

The previous prime is 204191003. The next prime is 204191027. The reversal of 204191021 is 120191402.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 179935396 + 24255625 = 13414^2 + 4925^2 .

It is a cyclic number.

It is not a de Polignac number, because 204191021 - 2¹⁴ = 204174637 is a prime.

It is a Chen prime.

It is a junction number, because it is equal to n+sod(n) for n = 204190984 and 204191002.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (204191027) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 102095510 + 102095511.

It is an arithmetic number, because the mean of its divisors is an integer number (102095511).

Almost surely, 2^204191021 is an apocalyptic number.

It is an amenable number.

204191021 is a deficient number, since it is larger than the sum of its proper divisors (1).

204191021 is an equidigital number, since it uses as much as digits as its factorization.

204191021 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 144, while the sum is 20.

The square root of 204191021 is about 14289.5423649605. The cubic root of 204191021 is about 588.8602155112.

The spelling of 204191021 in words is "two hundred four million, one hundred ninety-one thousand, twenty-one".