643641 has 8 divisors (see below), whose sum is σ = 870240. Its totient is φ = 423072.

The previous prime is 643639. The next prime is 643649. The reversal of 643641 is 146346.

643641 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 643641 - 2¹ = 643639 is a prime.

It is a nialpdrome in base 15.

It is not an unprimeable number, because it can be changed into a prime (643649) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1251 + ... + 1688.

It is an arithmetic number, because the mean of its divisors is an integer number (108780).

2⁶⁴³⁶⁴¹ is an apocalyptic number.

It is an amenable number.

643641 is a deficient number, since it is larger than the sum of its proper divisors (226599).

643641 is a wasteful number, since it uses less digits than its factorization.

643641 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3015.

The product of its digits is 1728, while the sum is 24.

The square root of 643641 is about 802.2723976306. The cubic root of 643641 is about 86.3405015175.

Adding to 643641 its reverse (146346), we get a palindrome (789987).

The spelling of 643641 in words is "six hundred forty-three thousand, six hundred forty-one".