6644389920 has 384 divisors, whose sum is σ = 24575975424. Its totient is φ = 1477730304.

The previous prime is 6644389919. The next prime is 6644390009. The reversal of 6644389920 is 299834466.

It is an unprimeable number.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 25263709 + ... + 25263971.

It is an arithmetic number, because the mean of its divisors is an integer number (63999936).

Almost surely, 2^6644389920 is an apocalyptic number.

6644389920 is a gapful number since it is divisible by the number (60) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 6644389920, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (12287987712).

6644389920 is an abundant number, since it is smaller than the sum of its proper divisors (17931585504).

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

6644389920 is a wasteful number, since it uses less digits than its factorization.

6644389920 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 464 (or 456 counting only the distinct ones).

The product of its (nonzero) digits is 2239488, while the sum is 51.

The square root of 6644389920 is about 81513.1272863457. The cubic root of 6644389920 is about 1879.9733963340.

The spelling of 6644389920 in words is "six billion, six hundred forty-four million, three hundred eighty-nine thousand, nine hundred twenty".