721440 has 96 divisors (see below), whose sum is σ = 2540160. Its totient is φ = 191232.

The previous prime is 721439. The next prime is 721451. The reversal of 721440 is 44127.

It is a happy number.

It is a tau number, because it is divible by the number of its divisors (96).

It is a Harshad number since it is a multiple of its sum of digits (18).

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (5) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 4237 + ... + 4403.

It is an arithmetic number, because the mean of its divisors is an integer number (26460).

2⁷²¹⁴⁴⁰ 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 721440, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1270080).

721440 is an abundant number, since it is smaller than the sum of its proper divisors (1818720).

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

721440 is a wasteful number, since it uses less digits than its factorization.

721440 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 191 (or 177 counting only the distinct ones).

The product of its (nonzero) digits is 224, while the sum is 18.

The square root of 721440 is about 849.3762417209. The cubic root of 721440 is about 89.6878072039.

Adding to 721440 its reverse (44127), we get a palindrome (765567).

The spelling of 721440 in words is "seven hundred twenty-one thousand, four hundred forty", and thus it is an iban number.