643806 has 24 divisors (see below), whose sum is σ = 1426464. Its totient is φ = 209760.

The previous prime is 643781. The next prime is 643847. The reversal of 643806 is 608346.

It is a Curzon number.

It is a self number, because there is not a number n which added to its sum of digits gives 643806.

It is a congruent number.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 643806.

It is an unprimeable number.

643806 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 11 ways as a sum of consecutive naturals, for example, 466 + ... + 1226.

It is an arithmetic number, because the mean of its divisors is an integer number (59436).

2⁶⁴³⁸⁰⁶ is an apocalyptic number.

643806 is an abundant number, since it is smaller than the sum of its proper divisors (782658).

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

643806 is a wasteful number, since it uses less digits than its factorization.

643806 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 816 (or 813 counting only the distinct ones).

The product of its (nonzero) digits is 3456, while the sum is 27.

The square root of 643806 is about 802.3752239445. The cubic root of 643806 is about 86.3478788006.

The spelling of 643806 in words is "six hundred forty-three thousand, eight hundred six".