643841 has 12 divisors (see below), whose sum is σ = 751716. Its totient is φ = 549120.

The previous prime is 643781. The next prime is 643847. The reversal of 643841 is 148346.

It can be written as a sum of positive squares in 2 ways, for example, as 193600 + 450241 = 440^2 + 671^2 .

It is not a de Polignac number, because 643841 - 2¹⁸ = 381697 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a self number, because there is not a number n which added to its sum of digits gives 643841.

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 11 ways as a sum of consecutive naturals, for example, 1901 + ... + 2213.

It is an arithmetic number, because the mean of its divisors is an integer number (62643).

2⁶⁴³⁸⁴¹ is an apocalyptic number.

It is an amenable number.

643841 is a deficient number, since it is larger than the sum of its proper divisors (107875).

643841 is a wasteful number, since it uses less digits than its factorization.

643841 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 352 (or 341 counting only the distinct ones).

The product of its digits is 2304, while the sum is 26.

The square root of 643841 is about 802.3970338928. The cubic root of 643841 is about 86.3494435168.

The spelling of 643841 in words is "six hundred forty-three thousand, eight hundred forty-one".