643257856 has 40 divisors (see below), whose sum is σ = 1316650104. Its totient is φ = 313774080.

The previous prime is 643257851. The next prime is 643257869. The reversal of 643257856 is 658752346.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (643257851) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 5671 + ... + 36313.

Almost surely, 2^643257856 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 643257856, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (658325052).

643257856 is an abundant number, since it is smaller than the sum of its proper divisors (673392248).

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

643257856 is an equidigital number, since it uses as much as digits as its factorization.

643257856 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 30702 (or 30686 counting only the distinct ones).

The product of its digits is 1209600, while the sum is 46.

The square root of 643257856 is about 25362.5285805655. The cubic root of 643257856 is about 863.2336597593.

The spelling of 643257856 in words is "six hundred forty-three million, two hundred fifty-seven thousand, eight hundred fifty-six".