721604309 has 2 divisors, whose sum is σ = 721604310. Its totient is φ = 721604308.

The previous prime is 721604293. The next prime is 721604357. The reversal of 721604309 is 903406127.

721604309 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 439028209 + 282576100 = 20953^2 + 16810^2 .

It is a cyclic number.

It is not a de Polignac number, because 721604309 - 2⁴ = 721604293 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (721604809) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 360802154 + 360802155.

It is an arithmetic number, because the mean of its divisors is an integer number (360802155).

Almost surely, 2^721604309 is an apocalyptic number.

It is an amenable number.

721604309 is a deficient number, since it is larger than the sum of its proper divisors (1).

721604309 is an equidigital number, since it uses as much as digits as its factorization.

721604309 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 9072, while the sum is 32.

The square root of 721604309 is about 26862.6936288973. The cubic root of 721604309 is about 896.9461552954.

The spelling of 721604309 in words is "seven hundred twenty-one million, six hundred four thousand, three hundred nine".