Adding to 721440 its reverse (44127), we get a palindrome (765567).
It is a happy number.
It is a tau number, because it is divible by the number of its divisors (96).
It is an unprimeable number.
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).
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 square root of 721440 is about 849.3762417209. The cubic root of 721440 is about 89.6878072039.
The spelling of 721440 in words is "seven hundred twenty-one thousand, four hundred forty", and thus it is an iban number.