721306656 has 216 divisors, whose sum is σ = 2420046720. Its totient is φ = 203164416.

The previous prime is 721306643. The next prime is 721306661. The reversal of 721306656 is 656603127.

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a self number, because there is not a number n which added to its sum of digits gives 721306656.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 35 ways as a sum of consecutive naturals, for example, 1114525 + ... + 1115171.

It is an arithmetic number, because the mean of its divisors is an integer number (11203920).

Almost surely, 2^721306656 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 721306656, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1210023360).

721306656 is an abundant number, since it is smaller than the sum of its proper divisors (1698740064).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

721306656 is a wasteful number, since it uses less digits than its factorization.

721306656 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 756 (or 738 counting only the distinct ones).

The product of its (nonzero) digits is 45360, while the sum is 36.

The square root of 721306656 is about 26857.1527902717. The cubic root of 721306656 is about 896.8228118751.

The spelling of 721306656 in words is "seven hundred twenty-one million, three hundred six thousand, six hundred fifty-six".