643958784 has 432 divisors, whose sum is σ = 2330415360. Its totient is φ = 170311680.

The previous prime is 643958719. The next prime is 643958789. The reversal of 643958784 is 487859346.

Its product of digits (5806080) is a multiple of the sum of its prime factors (96).

It is a self number, because there is not a number n which added to its sum of digits gives 643958784.

It is not an unprimeable number, because it can be changed into a prime (643958789) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 35 ways as a sum of consecutive naturals, for example, 20772849 + ... + 20772879.

It is an arithmetic number, because the mean of its divisors is an integer number (5394480).

Almost surely, 2^643958784 is an apocalyptic number.

643958784 is a gapful number since it is divisible by the number (64) 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 643958784, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1165207680).

643958784 is an abundant number, since it is smaller than the sum of its proper divisors (1686456576).

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

643958784 is a wasteful number, since it uses less digits than its factorization.

643958784 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 96 (or 66 counting only the distinct ones).

The product of its digits is 5806080, while the sum is 54.

The square root of 643958784 is about 25376.3429989429. The cubic root of 643958784 is about 863.5470877259.

The spelling of 643958784 in words is "six hundred forty-three million, nine hundred fifty-eight thousand, seven hundred eighty-four".