639646937 has 2 divisors, whose sum is σ = 639646938. Its totient is φ = 639646936.

The previous prime is 639646927. The next prime is 639646957. The reversal of 639646937 is 739646936.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 422261401 + 217385536 = 20549^2 + 14744^2 .

It is a cyclic number.

It is not a de Polignac number, because 639646937 - 2⁴ = 639646921 is a prime.

It is not a weakly prime, because it can be changed into another prime (639646927) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 319823468 + 319823469.

It is an arithmetic number, because the mean of its divisors is an integer number (319823469).

Almost surely, 2^639646937 is an apocalyptic number.

It is an amenable number.

639646937 is a deficient number, since it is larger than the sum of its proper divisors (1).

639646937 is an equidigital number, since it uses as much as digits as its factorization.

639646937 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 4408992, while the sum is 53.

The square root of 639646937 is about 25291.2422984716. The cubic root of 639646937 is about 861.6153778686.

Subtracting 639646937 from its reverse (739646936), we obtain a palindrome (99999999).

The spelling of 639646937 in words is "six hundred thirty-nine million, six hundred forty-six thousand, nine hundred thirty-seven".