6639918864 has 80 divisors (see below), whose sum is σ = 17723401344. Its totient is φ = 2140902400.

The previous prime is 6639918863. The next prime is 6639918907. The reversal of 6639918864 is 4688199366.

It is a junction number, because it is equal to n+sod(n) for n = 6639918798 and 6639918807.

It is not an unprimeable number, because it can be changed into a prime (6639918863) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 162244 + ... + 199004.

Almost surely, 2^6639918864 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 6639918864, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (8861700672).

6639918864 is an abundant number, since it is smaller than the sum of its proper divisors (11083482480).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

6639918864 is a wasteful number, since it uses less digits than its factorization.

6639918864 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 36896 (or 36890 counting only the distinct ones).

The product of its digits is 13436928, while the sum is 60.

The square root of 6639918864 is about 81485.6972971331. The cubic root of 6639918864 is about 1879.5516193409.

The spelling of 6639918864 in words is "six billion, six hundred thirty-nine million, nine hundred eighteen thousand, eight hundred sixty-four".