643823 has 6 divisors (see below), whose sum is σ = 661632. Its totient is φ = 626480.

The previous prime is 643781. The next prime is 643847. The reversal of 643823 is 328346.

It is not a de Polignac number, because 643823 - 2⁸ = 643567 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 643792 and 643801.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (643873) 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 5 ways as a sum of consecutive naturals, for example, 1490 + ... + 1872.

It is an arithmetic number, because the mean of its divisors is an integer number (110272).

2⁶⁴³⁸²³ is an apocalyptic number.

643823 is a deficient number, since it is larger than the sum of its proper divisors (17809).

643823 is an equidigital number, since it uses as much as digits as its factorization.

643823 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 465 (or 424 counting only the distinct ones).

The product of its digits is 3456, while the sum is 26.

The square root of 643823 is about 802.3858174220. The cubic root of 643823 is about 86.3486388127.

The spelling of 643823 in words is "six hundred forty-three thousand, eight hundred twenty-three".