725921521 has 4 divisors (see below), whose sum is σ = 781761652. Its totient is φ = 670081392.

The previous prime is 725921509. The next prime is 725921531. The reversal of 725921521 is 125129527.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 125129527 = 43 ⋅2909989.

It can be written as a sum of positive squares in 2 ways, for example, as 34810000 + 691111521 = 5900^2 + 26289^2 .

It is a cyclic number.

It is not a de Polignac number, because 725921521 - 2⁷ = 725921393 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (725921531) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 27920046 + ... + 27920071.

It is an arithmetic number, because the mean of its divisors is an integer number (195440413).

Almost surely, 2^725921521 is an apocalyptic number.

It is an amenable number.

725921521 is a deficient number, since it is larger than the sum of its proper divisors (55840131).

725921521 is a wasteful number, since it uses less digits than its factorization.

725921521 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 55840130.

The product of its digits is 12600, while the sum is 34.

The square root of 725921521 is about 26942.9308168209. The cubic root of 725921521 is about 898.7313487476.

The spelling of 725921521 in words is "seven hundred twenty-five million, nine hundred twenty-one thousand, five hundred twenty-one".