643857 has 8 divisors (see below), whose sum is σ = 864576. Its totient is φ = 426192.

The previous prime is 643849. The next prime is 643859. The reversal of 643857 is 758346.

643857 is digitally balanced in base 7, because in such base it contains all the possibile digits an equal number of times.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 643857 - 2³ = 643849 is a prime.

It is a Smith number, since the sum of its digits (33) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

643857 is strictly pandigital in base 7.

It is not an unprimeable number, because it can be changed into a prime (643859) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 213 + ... + 1154.

It is an arithmetic number, because the mean of its divisors is an integer number (108072).

2⁶⁴³⁸⁵⁷ is an apocalyptic number.

It is an amenable number.

643857 is a deficient number, since it is larger than the sum of its proper divisors (220719).

643857 is a wasteful number, since it uses less digits than its factorization.

643857 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1527.

The product of its digits is 20160, while the sum is 33.

The square root of 643857 is about 802.4070039575. The cubic root of 643857 is about 86.3501587967.

The spelling of 643857 in words is "six hundred forty-three thousand, eight hundred fifty-seven".