643775328 has 252 divisors, whose sum is σ = 2248269660. Its totient is φ = 174254976.

The previous prime is 643775269. The next prime is 643775333. The reversal of 643775328 is 823577346.

643775328 is a `hidden beast` number, since 6 + 43 + 77 + 532 + 8 = 666.

It is a tau number, because it is divible by the number of its divisors (252).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 41 ways as a sum of consecutive naturals, for example, 33882903 + ... + 33882921.

It is an arithmetic number, because the mean of its divisors is an integer number (8921705).

Almost surely, 2^643775328 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 643775328, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1124134830).

643775328 is an abundant number, since it is smaller than the sum of its proper divisors (1604494332).

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

643775328 is an frugal number, since it uses more digits than its factorization.

643775328 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 77 (or 31 counting only the distinct ones).

The product of its digits is 846720, while the sum is 45.

The square root of 643775328 is about 25372.7280362203. The cubic root of 643775328 is about 863.4650752612.

The spelling of 643775328 in words is "six hundred forty-three million, seven hundred seventy-five thousand, three hundred twenty-eight".