721684 has 12 divisors (see below), whose sum is σ = 1337364. Its totient is φ = 339584.

The previous prime is 721663. The next prime is 721687. The reversal of 721684 is 486127.

It can be written as a sum of positive squares in 2 ways, for example, as 672400 + 49284 = 820^2 + 222^2 .

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (721687) by changing a digit.

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, 5239 + ... + 5374.

It is an arithmetic number, because the mean of its divisors is an integer number (111447).

2⁷²¹⁶⁸⁴ is an apocalyptic number.

It is an amenable number.

721684 is a deficient number, since it is larger than the sum of its proper divisors (615680).

721684 is a wasteful number, since it uses less digits than its factorization.

721684 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10634 (or 10632 counting only the distinct ones).

The product of its digits is 2688, while the sum is 28.

The square root of 721684 is about 849.5198643940. The cubic root of 721684 is about 89.6979172423.

The spelling of 721684 in words is "seven hundred twenty-one thousand, six hundred eighty-four".