643638 has 8 divisors (see below), whose sum is σ = 1287288. Its totient is φ = 214544.

The previous prime is 643633. The next prime is 643639. The reversal of 643638 is 836346.

643638 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.

643638 is an admirable number.

It is an Ulam number.

It is a nialpdrome in base 15.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (643633) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 53631 + ... + 53642.

It is an arithmetic number, because the mean of its divisors is an integer number (160911).

2⁶⁴³⁶³⁸ is an apocalyptic number.

643638 is a primitive abundant number, since it is smaller than the sum of its proper divisors, none of which is abundant.

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

643638 is a wasteful number, since it uses less digits than its factorization.

643638 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 107278.

The product of its digits is 10368, while the sum is 30.

The square root of 643638 is about 802.2705279393. The cubic root of 643638 is about 86.3403673734.

The spelling of 643638 in words is "six hundred forty-three thousand, six hundred thirty-eight".