643238656 has 72 divisors (see below), whose sum is σ = 1382349024. Its totient is φ = 297615360.

The previous prime is 643238641. The next prime is 643238657. The reversal of 643238656 is 656832346.

It is not an unprimeable number, because it can be changed into a prime (643238657) 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, 264261 + ... + 266683.

It is an arithmetic number, because the mean of its divisors is an integer number (19199292).

Almost surely, 2^643238656 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 643238656, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (691174512).

643238656 is an abundant number, since it is smaller than the sum of its proper divisors (739110368).

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

643238656 is a wasteful number, since it uses less digits than its factorization.

643238656 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2517 (or 2503 counting only the distinct ones).

The product of its digits is 622080, while the sum is 43.

The square root of 643238656 is about 25362.1500665854. The cubic root of 643238656 is about 863.2250710568.

The spelling of 643238656 in words is "six hundred forty-three million, two hundred thirty-eight thousand, six hundred fifty-six".