664529221 has 2 divisors, whose sum is σ = 664529222. Its totient is φ = 664529220.

The previous prime is 664529219. The next prime is 664529227. The reversal of 664529221 is 122925466.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 609398596 + 55130625 = 24686^2 + 7425^2 .

It is a cyclic number.

It is not a de Polignac number, because 664529221 - 2¹ = 664529219 is a prime.

Together with 664529219, it forms a pair of twin primes.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (664529227) 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 as a sum of consecutive naturals, namely, 332264610 + 332264611.

It is an arithmetic number, because the mean of its divisors is an integer number (332264611).

Almost surely, 2^664529221 is an apocalyptic number.

It is an amenable number.

664529221 is a deficient number, since it is larger than the sum of its proper divisors (1).

664529221 is an equidigital number, since it uses as much as digits as its factorization.

664529221 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 51840, while the sum is 37.

The square root of 664529221 is about 25778.4642870750. The cubic root of 664529221 is about 872.6458497897.

The spelling of 664529221 in words is "six hundred sixty-four million, five hundred twenty-nine thousand, two hundred twenty-one".