643843 has 4 divisors (see below), whose sum is σ = 645480. Its totient is φ = 642208.

The previous prime is 643781. The next prime is 643847. The reversal of 643843 is 348346.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-643843 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (643847) 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, 171 + ... + 1147.

It is an arithmetic number, because the mean of its divisors is an integer number (161370).

2⁶⁴³⁸⁴³ is an apocalyptic number.

643843 is a deficient number, since it is larger than the sum of its proper divisors (1637).

643843 is an equidigital number, since it uses as much as digits as its factorization.

643843 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1636.

The product of its digits is 6912, while the sum is 28.

The square root of 643843 is about 802.3982801577. The cubic root of 643843 is about 86.3495329274.

The spelling of 643843 in words is "six hundred forty-three thousand, eight hundred forty-three".