725709721 has 27 divisors (see below), whose sum is σ = 834808149. Its totient is φ = 630372600.

The previous prime is 725709713. The next prime is 725709737. The reversal of 725709721 is 127907527.

It is a happy number.

The square root of 725709721 is 26939.

It is a perfect power (a square), and thus also a powerful number.

725709721 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 725709721 - 2³ = 725709713 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (725709781) by changing a digit.

It is a polite number, since it can be written in 26 ways as a sum of consecutive naturals, for example, 9186160 + ... + 9186238.

Almost surely, 2^725709721 is an apocalyptic number.

725709721 is the 26939-th square number.

725709721 is the 13470-th centered octagonal number.

It is an amenable number.

725709721 is a deficient number, since it is larger than the sum of its proper divisors (109098428).

725709721 is an equidigital number, since it uses as much as digits as its factorization.

725709721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 242 (or 121 counting only the distinct ones).

The product of its (nonzero) digits is 61740, while the sum is 40.

The cubic root of 725709721 is about 898.6439335060.

The spelling of 725709721 in words is "seven hundred twenty-five million, seven hundred nine thousand, seven hundred twenty-one".