721393920 has 216 divisors, whose sum is σ = 2688501816. Its totient is φ = 177537024.

The previous prime is 721393877. The next prime is 721393927. The reversal of 721393920 is 29393127.

721393920 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It can be written as a sum of positive squares in 4 ways, for example, as 9144576 + 712249344 = 3024^2 + 26688^2 .

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

It is not an unprimeable number, because it can be changed into a prime (721393927) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 147352 + ... + 152168.

Almost surely, 2^721393920 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 721393920, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1344250908).

721393920 is an abundant number, since it is smaller than the sum of its proper divisors (1967107896).

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

721393920 is a wasteful number, since it uses less digits than its factorization.

721393920 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4857 (or 4840 counting only the distinct ones).

The product of its (nonzero) digits is 20412, while the sum is 36.

The square root of 721393920 is about 26858.7773362825. Note that the first 3 decimals coincide. The cubic root of 721393920 is about 896.8589764242.

The spelling of 721393920 in words is "seven hundred twenty-one million, three hundred ninety-three thousand, nine hundred twenty".