721604 has 12 divisors (see below), whose sum is σ = 1360044. Its totient is φ = 333024.

The previous prime is 721597. The next prime is 721613. The reversal of 721604 is 406127.

It can be written as a sum of positive squares in 2 ways, for example, as 78400 + 643204 = 280^2 + 802^2 .

It is an Ulam number.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 721604.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 6887 + ... + 6990.

It is an arithmetic number, because the mean of its divisors is an integer number (113337).

2⁷²¹⁶⁰⁴ is an apocalyptic number.

It is an amenable number.

721604 is a deficient number, since it is larger than the sum of its proper divisors (638440).

721604 is a wasteful number, since it uses less digits than its factorization.

721604 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 13894 (or 13892 counting only the distinct ones).

The product of its (nonzero) digits is 336, while the sum is 20.

The square root of 721604 is about 849.4727776686. The cubic root of 721604 is about 89.6946027268.

The spelling of 721604 in words is "seven hundred twenty-one thousand, six hundred four".