643836 has 12 divisors (see below), whose sum is σ = 1502312. Its totient is φ = 214608.

The previous prime is 643781. The next prime is 643847. The reversal of 643836 is 638346.

It is a tau number, because it is divible by the number of its divisors (12).

It is a d-powerful number, because it can be written as 6⁶ + 4⁷ + 8³ + 3⁷ + 3¹² + 6⁶ .

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 26815 + ... + 26838.

2⁶⁴³⁸³⁶ is an apocalyptic number.

It is an amenable number.

643836 is an abundant number, since it is smaller than the sum of its proper divisors (858476).

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

643836 is a wasteful number, since it uses less digits than its factorization.

643836 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 53660 (or 53658 counting only the distinct ones).

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

The square root of 643836 is about 802.3939182222. The cubic root of 643836 is about 86.3492199894.

The spelling of 643836 in words is "six hundred forty-three thousand, eight hundred thirty-six".