643838 has 8 divisors (see below), whose sum is σ = 1040088. Its totient is φ = 297144.

The previous prime is 643781. The next prime is 643847. The reversal of 643838 is 838346.

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

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 12356 + ... + 12407.

It is an arithmetic number, because the mean of its divisors is an integer number (130011).

2⁶⁴³⁸³⁸ is an apocalyptic number.

643838 is a deficient number, since it is larger than the sum of its proper divisors (396250).

643838 is a wasteful number, since it uses less digits than its factorization.

643838 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 24778.

The product of its digits is 13824, while the sum is 32.

The square root of 643838 is about 802.3951644919. The cubic root of 643838 is about 86.3493094005.

The spelling of 643838 in words is "six hundred forty-three thousand, eight hundred thirty-eight".