643355856 has 240 divisors, whose sum is σ = 2139446400. Its totient is φ = 177914880.

The previous prime is 643355851. The next prime is 643355857. The reversal of 643355856 is 658553346.

643355856 is a `hidden beast` number, since 6 + 43 + 3 + 558 + 56 = 666.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (643355851) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 3232845 + ... + 3233043.

It is an arithmetic number, because the mean of its divisors is an integer number (8914360).

Almost surely, 2^643355856 is an apocalyptic number.

643355856 is a gapful number since it is divisible by the number (66) 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 643355856, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1069723200).

643355856 is an abundant number, since it is smaller than the sum of its proper divisors (1496090544).

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

643355856 is a wasteful number, since it uses less digits than its factorization.

643355856 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 394 (or 385 counting only the distinct ones).

The product of its digits is 1296000, while the sum is 45.

The square root of 643355856 is about 25364.4604910099. The cubic root of 643355856 is about 863.2774952664.

The spelling of 643355856 in words is "six hundred forty-three million, three hundred fifty-five thousand, eight hundred fifty-six".