6639985280 has 64 divisors (see below), whose sum is σ = 15894307080. Its totient is φ = 2652549120.

The previous prime is 6639985267. The next prime is 6639985283. The reversal of 6639985280 is 825899366.

It can be written as a sum of positive squares in 4 ways, for example, as 3115425856 + 3524559424 = 55816^2 + 59368^2 .

It is a tau number, because it is divible by the number of its divisors (64).

It is not an unprimeable number, because it can be changed into a prime (6639985283) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 519122 + ... + 531758.

Almost surely, 2^6639985280 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 6639985280, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (7947153540).

6639985280 is an abundant number, since it is smaller than the sum of its proper divisors (9254321800).

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

6639985280 is a wasteful number, since it uses less digits than its factorization.

6639985280 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 13477 (or 13465 counting only the distinct ones).

The product of its (nonzero) digits is 5598720, while the sum is 56.

The square root of 6639985280 is about 81486.1048277558. The cubic root of 6639985280 is about 1879.5578860783.

The spelling of 6639985280 in words is "six billion, six hundred thirty-nine million, nine hundred eighty-five thousand, two hundred eighty".