639205989844 has 12 divisors (see below), whose sum is σ = 1118659335444. Its totient is φ = 319589036864.

The previous prime is 639205989833. The next prime is 639205989883. The reversal of 639205989844 is 448989502936.

It can be written as a sum of positive squares in 2 ways, for example, as 156475624900 + 482730364944 = 395570^2 + 694788^2 .

It is a super-2 number, since 2×639205989844² (a number of 24 digits) contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 639205989844.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3386137 + ... + 3569920.

It is an arithmetic number, because the mean of its divisors is an integer number (93221611287).

Almost surely, 2^639205989844 is an apocalyptic number.

It is an amenable number.

639205989844 is a deficient number, since it is larger than the sum of its proper divisors (479453345600).

639205989844 is a wasteful number, since it uses less digits than its factorization.

639205989844 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6979034 (or 6979032 counting only the distinct ones).

The product of its (nonzero) digits is 134369280, while the sum is 67.

The spelling of 639205989844 in words is "six hundred thirty-nine billion, two hundred five million, nine hundred eighty-nine thousand, eight hundred forty-four".