728721 has 24 divisors (see below), whose sum is σ = 1235520. Its totient is φ = 405216.

The previous prime is 728713. The next prime is 728723. The reversal of 728721 is 127827.

728721 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is not a de Polignac number, because 728721 - 2³ = 728713 is a prime.

728721 is a lucky number.

It is not an unprimeable number, because it can be changed into a prime (728723) 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, 2575 + ... + 2843.

It is an arithmetic number, because the mean of its divisors is an integer number (51480).

2⁷²⁸⁷²¹ is an apocalyptic number.

It is an amenable number.

728721 is a deficient number, since it is larger than the sum of its proper divisors (506799).

728721 is a wasteful number, since it uses less digits than its factorization.

728721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 325 (or 322 counting only the distinct ones).

The product of its digits is 1568, while the sum is 27.

The square root of 728721 is about 853.6515682642. The cubic root of 728721 is about 89.9885170535.

The spelling of 728721 in words is "seven hundred twenty-eight thousand, seven hundred twenty-one".