643688 has 16 divisors (see below), whose sum is σ = 1278180. Its totient is φ = 302848.

The previous prime is 643681. The next prime is 643691. The reversal of 643688 is 886346.

It can be written as a sum of positive squares in 2 ways, for example, as 643204 + 484 = 802^2 + 22^2 .

It is not an unprimeable number, because it can be changed into a prime (643681) by changing a digit.

643688 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 3 ways as a sum of consecutive naturals, for example, 2231 + ... + 2502.

2⁶⁴³⁶⁸⁸ is an apocalyptic number.

643688 is a gapful number since it is divisible by the number (68) formed by its first and last digit.

It is an amenable number.

643688 is a deficient number, since it is larger than the sum of its proper divisors (634492).

643688 is a wasteful number, since it uses less digits than its factorization.

643688 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4756 (or 4752 counting only the distinct ones).

The product of its digits is 27648, while the sum is 35.

The square root of 643688 is about 802.3016888927. The cubic root of 643688 is about 86.3426030538.

It can be divided in two parts, 643 and 688, that added together give a palindrome (1331).

The spelling of 643688 in words is "six hundred forty-three thousand, six hundred eighty-eight".