643844 has 12 divisors (see below), whose sum is σ = 1148364. Its totient is φ = 315744.

The previous prime is 643781. The next prime is 643847. The reversal of 643844 is 448346.

It can be written as a sum of positive squares in 2 ways, for example, as 506944 + 136900 = 712^2 + 370^2 .

It is not an unprimeable number, because it can be changed into a prime (643847) by changing a digit.

643844 is an untouchable number, because it is not equal to the sum of proper divisors of any number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1307 + ... + 1730.

It is an arithmetic number, because the mean of its divisors is an integer number (95697).

2⁶⁴³⁸⁴⁴ is an apocalyptic number.

It is an amenable number.

643844 is a deficient number, since it is larger than the sum of its proper divisors (504520).

643844 is a wasteful number, since it uses less digits than its factorization.

643844 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3094 (or 3092 counting only the distinct ones).

The product of its digits is 9216, while the sum is 29.

The square root of 643844 is about 802.3989032894. The cubic root of 643844 is about 86.3495776327.

It can be divided in two parts, 64 and 3844, that multiplied together give a square (246016 = 496²).

The spelling of 643844 in words is "six hundred forty-three thousand, eight hundred forty-four".