209664 has 108 divisors (see below), whose sum is σ = 744016. Its totient is φ = 55296.

The previous prime is 209659. The next prime is 209669. The reversal of 209664 is 466902.

It is an interprime number because it is at equal distance from previous prime (209659) and next prime (209669).

It is a nialpdrome in base 16.

It is a zygodrome in base 2 and base 16.

It is not an unprimeable number, because it can be changed into a prime (209669) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 16122 + ... + 16134.

2²⁰⁹⁶⁶⁴ is an apocalyptic number.

209664 is a gapful number since it is divisible by the number (24) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 209664, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (372008).

209664 is an abundant number, since it is smaller than the sum of its proper divisors (534352).

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

209664 is a wasteful number, since it uses less digits than its factorization.

209664 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 42 (or 25 counting only the distinct ones).

The product of its (nonzero) digits is 2592, while the sum is 27.

The square root of 209664 is about 457.8908166801. The cubic root of 209664 is about 59.4075016883.

The spelling of 209664 in words is "two hundred nine thousand, six hundred sixty-four".