643908 has 24 divisors (see below), whose sum is σ = 1568448. Its totient is φ = 205216.

The previous prime is 643889. The next prime is 643919. The reversal of 643908 is 809346.

It is an unprimeable number.

643908 is an untouchable number, because it is not equal to the sum of proper divisors of any number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 891 + ... + 1442.

It is an arithmetic number, because the mean of its divisors is an integer number (65352).

2⁶⁴³⁹⁰⁸ is an apocalyptic number.

It is an amenable number.

643908 is an abundant number, since it is smaller than the sum of its proper divisors (924540).

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

643908 is a wasteful number, since it uses less digits than its factorization.

643908 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2363 (or 2361 counting only the distinct ones).

The product of its (nonzero) digits is 5184, while the sum is 30.

The square root of 643908 is about 802.4387827118. The cubic root of 643908 is about 86.3524386724.

It can be divided in two parts, 643 and 908, that added together give a palindrome (1551).

The spelling of 643908 in words is "six hundred forty-three thousand, nine hundred eight".