721856 has 14 divisors (see below), whose sum is σ = 1432560. Its totient is φ = 360896.

The previous prime is 721849. The next prime is 721859. The reversal of 721856 is 658127.

It is an alternating number because its digits alternate between odd and even.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (721859) 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 as a sum of consecutive naturals, namely, 5576 + ... + 5703.

2⁷²¹⁸⁵⁶ is an apocalyptic number.

It is an amenable number.

721856 is a deficient number, since it is larger than the sum of its proper divisors (710704).

721856 is a wasteful number, since it uses less digits than its factorization.

721856 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 11291 (or 11281 counting only the distinct ones).

The product of its digits is 3360, while the sum is 29.

The square root of 721856 is about 849.6210920169. The cubic root of 721856 is about 89.7050426214.

The spelling of 721856 in words is "seven hundred twenty-one thousand, eight hundred fifty-six".