721920 has 88 divisors (see below), whose sum is σ = 2358144. Its totient is φ = 188416.

The previous prime is 721909. The next prime is 721921. The reversal of 721920 is 29127.

It is a happy number.

It is a hoax number, since the sum of its digits (21) coincides with the sum of the digits of its distinct prime factors.

It is not an unprimeable number, because it can be changed into a prime (721921) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 15337 + ... + 15383.

2⁷²¹⁹²⁰ 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 721920, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1179072).

721920 is an abundant number, since it is smaller than the sum of its proper divisors (1636224).

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

721920 is a wasteful number, since it uses less digits than its factorization.

721920 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 75 (or 57 counting only the distinct ones).

The product of its (nonzero) digits is 252, while the sum is 21.

The square root of 721920 is about 849.6587550305. The cubic root of 721920 is about 89.7076936363.

The spelling of 721920 in words is "seven hundred twenty-one thousand, nine hundred twenty".