643835728 has 40 divisors (see below), whose sum is σ = 1292807880. Its totient is φ = 310248960.

The previous prime is 643835723. The next prime is 643835737. The reversal of 643835728 is 827538346.

It can be written as a sum of positive squares in 4 ways, for example, as 300304 + 643535424 = 548^2 + 25368^2 .

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (643835723) 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 7 ways as a sum of consecutive naturals, for example, 368938 + ... + 370678.

It is an arithmetic number, because the mean of its divisors is an integer number (32320197).

Almost surely, 2^643835728 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 643835728, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (646403940).

643835728 is an abundant number, since it is smaller than the sum of its proper divisors (648972152).

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

643835728 is a wasteful number, since it uses less digits than its factorization.

643835728 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2575 (or 2569 counting only the distinct ones).

The product of its digits is 967680, while the sum is 46.

The square root of 643835728 is about 25373.9182626570. The cubic root of 643835728 is about 863.4920782944.

The spelling of 643835728 in words is "six hundred forty-three million, eight hundred thirty-five thousand, seven hundred twenty-eight".