209640 has 32 divisors (see below), whose sum is σ = 629280. Its totient is φ = 55872.

The previous prime is 209639. The next prime is 209647. The reversal of 209640 is 46902.

209640 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is not an unprimeable number, because it can be changed into a prime (209647) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 754 + ... + 993.

It is an arithmetic number, because the mean of its divisors is an integer number (19665).

2²⁰⁹⁶⁴⁰ is an apocalyptic number.

209640 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

209640 is an abundant number, since it is smaller than the sum of its proper divisors (419640).

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

209640 is a wasteful number, since it uses less digits than its factorization.

209640 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1761 (or 1757 counting only the distinct ones).

The product of its (nonzero) digits is 432, while the sum is 21.

The square root of 209640 is about 457.8646088092. The cubic root of 209640 is about 59.4052348321.

The spelling of 209640 in words is "two hundred nine thousand, six hundred forty".