204721721 has 2 divisors, whose sum is σ = 204721722. Its totient is φ = 204721720.

The previous prime is 204721687. The next prime is 204721739. The reversal of 204721721 is 127127402.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 203376121 + 1345600 = 14261^2 + 1160^2 .

It is a cyclic number.

It is not a de Polignac number, because 204721721 - 2¹⁴ = 204705337 is a prime.

It is not a weakly prime, because it can be changed into another prime (204721921) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 102360860 + 102360861.

It is an arithmetic number, because the mean of its divisors is an integer number (102360861).

Almost surely, 2^204721721 is an apocalyptic number.

It is an amenable number.

204721721 is a deficient number, since it is larger than the sum of its proper divisors (1).

204721721 is an equidigital number, since it uses as much as digits as its factorization.

204721721 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 1568, while the sum is 26.

The square root of 204721721 is about 14308.0998389024. The cubic root of 204721721 is about 589.3699306545.

The spelling of 204721721 in words is "two hundred four million, seven hundred twenty-one thousand, seven hundred twenty-one".