720312521 has 4 divisors (see below), whose sum is σ = 723182544. Its totient is φ = 717442500.

The previous prime is 720312451. The next prime is 720312563. The reversal of 720312521 is 125213027.

It is a happy number.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-720312521 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (720312581) 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, 1434635 + ... + 1435136.

It is an arithmetic number, because the mean of its divisors is an integer number (180795636).

Almost surely, 2^720312521 is an apocalyptic number.

It is an amenable number.

720312521 is a deficient number, since it is larger than the sum of its proper divisors (2870023).

720312521 is a wasteful number, since it uses less digits than its factorization.

720312521 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2870022.

The product of its (nonzero) digits is 840, while the sum is 23.

The square root of 720312521 is about 26838.6385832069. The cubic root of 720312521 is about 896.4106095433.

Adding to 720312521 its reverse (125213027), we get a palindrome (845525548).

The spelling of 720312521 in words is "seven hundred twenty million, three hundred twelve thousand, five hundred twenty-one".