217664 has 28 divisors (see below), whose sum is σ = 457200. Its totient is φ = 102528.

The previous prime is 217661. The next prime is 217667. The reversal of 217664 is 466712.

217664 is digitally balanced in base 3, because in such base it contains all the possibile digits an equal number of times.

It is an interprime number because it is at equal distance from previous prime (217661) and next prime (217667).

It is a nialpdrome in base 8.

It is not an unprimeable number, because it can be changed into a prime (217661) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1127 + ... + 1305.

2²¹⁷⁶⁶⁴ is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 217664, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (228600).

217664 is an abundant number, since it is smaller than the sum of its proper divisors (239536).

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

217664 is a wasteful number, since it uses less digits than its factorization.

217664 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 210 (or 200 counting only the distinct ones).

The product of its digits is 2016, while the sum is 26.

The square root of 217664 is about 466.5447459783. The cubic root of 217664 is about 60.1536801117.

The spelling of 217664 in words is "two hundred seventeen thousand, six hundred sixty-four".