643209 has 16 divisors (see below), whose sum is σ = 992640. Its totient is φ = 362880.

The previous prime is 643199. The next prime is 643213. The reversal of 643209 is 902346.

It is not a de Polignac number, because 643209 - 2⁷ = 643081 is a prime.

It is a Curzon number.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 643209.

It is not an unprimeable number, because it can be changed into a prime (643009) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 2149 + ... + 2429.

It is an arithmetic number, because the mean of its divisors is an integer number (62040).

2⁶⁴³²⁰⁹ is an apocalyptic number.

It is an amenable number.

643209 is a deficient number, since it is larger than the sum of its proper divisors (349431).

643209 is a wasteful number, since it uses less digits than its factorization.

643209 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 400.

The product of its (nonzero) digits is 1296, while the sum is 24.

The square root of 643209 is about 802.0031172009. The cubic root of 643209 is about 86.3211804754.

The spelling of 643209 in words is "six hundred forty-three thousand, two hundred nine".