639447813 has 6 divisors (see below), whose sum is σ = 923646854. Its totient is φ = 426298536.

The previous prime is 639447791. The next prime is 639447821. The reversal of 639447813 is 318744936.

639447813 is a `hidden beast` number, since 639 + 4 + 4 + 7 + 8 + 1 + 3 = 666.

It can be written as a sum of positive squares in only one way, i.e., 510443649 + 129004164 = 22593^2 + 11358^2 .

It is not a de Polignac number, because 639447813 - 2⁶ = 639447749 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (639447113) 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 in 5 ways as a sum of consecutive naturals, for example, 35524870 + ... + 35524887.

Almost surely, 2^639447813 is an apocalyptic number.

It is an amenable number.

639447813 is a deficient number, since it is larger than the sum of its proper divisors (284199041).

639447813 is a wasteful number, since it uses less digits than its factorization.

639447813 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 71049763 (or 71049760 counting only the distinct ones).

The product of its digits is 435456, while the sum is 45.

The square root of 639447813 is about 25287.3053724591. The cubic root of 639447813 is about 861.5259607768.

The spelling of 639447813 in words is "six hundred thirty-nine million, four hundred forty-seven thousand, eight hundred thirteen".