720521 has 4 divisors (see below), whose sum is σ = 751872. Its totient is φ = 689172.

The previous prime is 720497. The next prime is 720527. The reversal of 720521 is 125027.

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 not a de Polignac number, because 720521 - 2¹⁸ = 458377 is a prime.

It is a super-2 number, since 2×720521² = 1038301022882, which contains 22 as substring.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 720521.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 720521.

It is not an unprimeable number, because it can be changed into a prime (720527) 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, 15641 + ... + 15686.

It is an arithmetic number, because the mean of its divisors is an integer number (187968).

2⁷²⁰⁵²¹ is an apocalyptic number.

It is an amenable number.

720521 is a deficient number, since it is larger than the sum of its proper divisors (31351).

720521 is a wasteful number, since it uses less digits than its factorization.

720521 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 31350.

The product of its (nonzero) digits is 140, while the sum is 17.

The square root of 720521 is about 848.8350841006. The cubic root of 720521 is about 89.6497083472.

Adding to 720521 its reverse (125027), we get a palindrome (845548).

The spelling of 720521 in words is "seven hundred twenty thousand, five hundred twenty-one".