643869 has 10 divisors (see below), whose sum is σ = 961950. Its totient is φ = 429192.

The previous prime is 643859. The next prime is 643873. The reversal of 643869 is 968346.

643869 is a `hidden beast` number, since 643 + 8 + 6 + 9 = 666.

It can be written as a sum of positive squares in only one way, i.e., 544644 + 99225 = 738^2 + 315^2 .

It is not a de Polignac number, because 643869 - 2¹¹ = 641821 is a prime.

It is a super-2 number, since 2×643869² = 829134578322, which contains 22 as substring.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (643849) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 9 ways as a sum of consecutive naturals, for example, 3894 + ... + 4055.

It is an arithmetic number, because the mean of its divisors is an integer number (96195).

2⁶⁴³⁸⁶⁹ is an apocalyptic number.

It is an amenable number.

643869 is a deficient number, since it is larger than the sum of its proper divisors (318081).

643869 is an equidigital number, since it uses as much as digits as its factorization.

643869 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7961 (or 7952 counting only the distinct ones).

The product of its digits is 31104, while the sum is 36.

The square root of 643869 is about 802.4144814247. The cubic root of 643869 is about 86.3506952489.

The spelling of 643869 in words is "six hundred forty-three thousand, eight hundred sixty-nine".