643831 has 4 divisors (see below), whose sum is σ = 651672. Its totient is φ = 635992.

The previous prime is 643781. The next prime is 643847. The reversal of 643831 is 138346.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 643831 - 2⁷ = 643703 is a prime.

It is a super-2 number, since 2×643831² = 829036713122, which contains 22 as substring.

It is an Ulam number.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 643796 and 643805.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (643031) 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 3 ways as a sum of consecutive naturals, for example, 3796 + ... + 3961.

It is an arithmetic number, because the mean of its divisors is an integer number (162918).

2⁶⁴³⁸³¹ is an apocalyptic number.

643831 is a deficient number, since it is larger than the sum of its proper divisors (7841).

643831 is an equidigital number, since it uses as much as digits as its factorization.

643831 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7840.

The product of its digits is 1728, while the sum is 25.

The square root of 643831 is about 802.3908025395. The cubic root of 643831 is about 86.3489964608.

The spelling of 643831 in words is "six hundred forty-three thousand, eight hundred thirty-one".