664043521 has 8 divisors (see below), whose sum is σ = 704098080. Its totient is φ = 624499488.

The previous prime is 664043459. The next prime is 664043531. The reversal of 664043521 is 125340466.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 664043521 - 2¹³ = 664035329 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (664043531) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 124951 + ... + 130156.

It is an arithmetic number, because the mean of its divisors is an integer number (88012260).

It is a Proth number, since it is equal to 20265 ⋅ 2¹⁵ + 1 and 20265 < 2¹⁵.

Almost surely, 2^664043521 is an apocalyptic number.

It is an amenable number.

664043521 is a deficient number, since it is larger than the sum of its proper divisors (40054559).

664043521 is a wasteful number, since it uses less digits than its factorization.

664043521 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 255263.

The product of its (nonzero) digits is 17280, while the sum is 31.

The square root of 664043521 is about 25769.0419107890. The cubic root of 664043521 is about 872.4331942840.

Adding to 664043521 its reverse (125340466), we get a palindrome (789383987).

The spelling of 664043521 in words is "six hundred sixty-four million, forty-three thousand, five hundred twenty-one".