6438721920 has 256 divisors, whose sum is σ = 21097843200. Its totient is φ = 1669627904.

The previous prime is 6438721903. The next prime is 6438721931. The reversal of 6438721920 is 291278346.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 12800389 + ... + 12800891.

It is an arithmetic number, because the mean of its divisors is an integer number (82413450).

Almost surely, 2^6438721920 is an apocalyptic number.

6438721920 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 6438721920, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (10548921600).

6438721920 is an abundant number, since it is smaller than the sum of its proper divisors (14659121280).

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

6438721920 is a wasteful number, since it uses less digits than its factorization.

6438721920 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 697 (or 685 counting only the distinct ones).

The product of its (nonzero) digits is 145152, while the sum is 42.

The square root of 6438721920 is about 80241.6470419196. The cubic root of 6438721920 is about 1860.3724077997.

The spelling of 6438721920 in words is "six billion, four hundred thirty-eight million, seven hundred twenty-one thousand, nine hundred twenty".