664521 has 16 divisors (see below), whose sum is σ = 1041600. Its totient is φ = 371520.

The previous prime is 664511. The next prime is 664529. The reversal of 664521 is 125466.

It is not a de Polignac number, because 664521 - 2⁹ = 664009 is a prime.

It is a super-3 number, since 3×664521³ = 880333815899678283, which contains 333 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 664491 and 664500.

It is not an unprimeable number, because it can be changed into a prime (664529) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 346 + ... + 1203.

It is an arithmetic number, because the mean of its divisors is an integer number (65100).

2⁶⁶⁴⁵²¹ is an apocalyptic number.

It is an amenable number.

664521 is a deficient number, since it is larger than the sum of its proper divisors (377079).

664521 is a wasteful number, since it uses less digits than its factorization.

664521 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1576.

The product of its digits is 1440, while the sum is 24.

The square root of 664521 is about 815.1815748654. The cubic root of 664521 is about 87.2642251227.

Adding to 664521 its reverse (125466), we get a palindrome (789987).

It can be divided in two parts, 6645 and 21, that added together give a palindrome (6666).

The spelling of 664521 in words is "six hundred sixty-four thousand, five hundred twenty-one".