643403920 has 80 divisors (see below), whose sum is σ = 1526009472. Its totient is φ = 252241920.

The previous prime is 643403861. The next prime is 643403921. The reversal of 643403920 is 29304346.

643403920 is digitally balanced in base 6, because in such base it contains all the possibile digits an equal number of times.

It is a tau number, because it is divible by the number of its divisors (80).

It is not an unprimeable number, because it can be changed into a prime (643403921) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 930775 + ... + 931465.

Almost surely, 2^643403920 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 643403920, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (763004736).

643403920 is an abundant number, since it is smaller than the sum of its proper divisors (882605552).

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

643403920 is a wasteful number, since it uses less digits than its factorization.

643403920 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 920 (or 914 counting only the distinct ones).

The product of its (nonzero) digits is 15552, while the sum is 31.

The square root of 643403920 is about 25365.4079407369. The cubic root of 643403920 is about 863.2989927192.

The spelling of 643403920 in words is "six hundred forty-three million, four hundred three thousand, nine hundred twenty".