204721921 has 2 divisors, whose sum is σ = 204721922. Its totient is φ = 204721920.

The previous prime is 204721901. The next prime is 204721927. The reversal of 204721921 is 129127402.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 170041600 + 34680321 = 13040^2 + 5889^2 .

It is a cyclic number.

It is not a de Polignac number, because 204721921 - 2¹¹ = 204719873 is a prime.

It is a super-2 number, since 2×204721921² = 83822129875860482, which contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 204721921.

It is not a weakly prime, because it can be changed into another prime (204721927) 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, 102360960 + 102360961.

It is an arithmetic number, because the mean of its divisors is an integer number (102360961).

Almost surely, 2^204721921 is an apocalyptic number.

It is an amenable number.

204721921 is a deficient number, since it is larger than the sum of its proper divisors (1).

204721921 is an equidigital number, since it uses as much as digits as its factorization.

204721921 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 2016, while the sum is 28.

The square root of 204721921 is about 14308.1068279490. The cubic root of 204721921 is about 589.3701225800.

The spelling of 204721921 in words is "two hundred four million, seven hundred twenty-one thousand, nine hundred twenty-one".