639664057 has 2 divisors, whose sum is σ = 639664058. Its totient is φ = 639664056.

The previous prime is 639664043. The next prime is 639664111. The reversal of 639664057 is 750466936.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 442008576 + 197655481 = 21024^2 + 14059^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-639664057 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 639663998 and 639664016.

It is not a weakly prime, because it can be changed into another prime (639667057) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 319832028 + 319832029.

It is an arithmetic number, because the mean of its divisors is an integer number (319832029).

Almost surely, 2^639664057 is an apocalyptic number.

It is an amenable number.

639664057 is a deficient number, since it is larger than the sum of its proper divisors (1).

639664057 is an equidigital number, since it uses as much as digits as its factorization.

639664057 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 816480, while the sum is 46.

The square root of 639664057 is about 25291.5807532863. The cubic root of 639664057 is about 861.6230647778.

The spelling of 639664057 in words is "six hundred thirty-nine million, six hundred sixty-four thousand, fifty-seven".