664513221 has 16 divisors (see below), whose sum is σ = 970488000. Its totient is φ = 402571008.

The previous prime is 664513219. The next prime is 664513231. The reversal of 664513221 is 122315466.

It is not a de Polignac number, because 664513221 - 2¹ = 664513219 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (664513231) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 223171 + ... + 226128.

It is an arithmetic number, because the mean of its divisors is an integer number (60655500).

Almost surely, 2^664513221 is an apocalyptic number.

It is an amenable number.

664513221 is a deficient number, since it is larger than the sum of its proper divisors (305974779).

664513221 is a wasteful number, since it uses less digits than its factorization.

664513221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 449348.

The product of its digits is 8640, while the sum is 30.

The square root of 664513221 is about 25778.1539486442. The cubic root of 664513221 is about 872.6388461119.

Adding to 664513221 its reverse (122315466), we get a palindrome (786828687).

The spelling of 664513221 in words is "six hundred sixty-four million, five hundred thirteen thousand, two hundred twenty-one".