664321639 has 2 divisors, whose sum is σ = 664321640. Its totient is φ = 664321638.

The previous prime is 664321607. The next prime is 664321667. The reversal of 664321639 is 936123466.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 664321639 - 2⁵ = 664321607 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (664321139) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 332160819 + 332160820.

It is an arithmetic number, because the mean of its divisors is an integer number (332160820).

Almost surely, 2^664321639 is an apocalyptic number.

664321639 is a deficient number, since it is larger than the sum of its proper divisors (1).

664321639 is an equidigital number, since it uses as much as digits as its factorization.

664321639 is an evil number, because the sum of its binary digits is even.

The product of its digits is 139968, while the sum is 40.

The square root of 664321639 is about 25774.4377048269. The cubic root of 664321639 is about 872.5549762158.

It can be divided in two parts, 6643 and 21639, that added together give a palindrome (28282).

The spelling of 664321639 in words is "six hundred sixty-four million, three hundred twenty-one thousand, six hundred thirty-nine".