216684 has 36 divisors (see below), whose sum is σ = 591136. Its totient is φ = 66528.

The previous prime is 216679. The next prime is 216703. The reversal of 216684 is 486612.

It is a tau number, because it is divible by the number of its divisors (36).

It is a Smith number, since the sum of its digits (27) coincides with the sum of the digits of its prime factors.

It is an unprimeable number.

216684 is an untouchable number, because it is not equal to the sum of proper divisors of any number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 237 + ... + 699.

2²¹⁶⁶⁸⁴ 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 216684, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (295568).

216684 is an abundant number, since it is smaller than the sum of its proper divisors (374452).

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

216684 is a wasteful number, since it uses less digits than its factorization.

216684 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 486 (or 481 counting only the distinct ones).

The product of its digits is 2304, while the sum is 27.

The square root of 216684 is about 465.4932867400. The cubic root of 216684 is about 60.0632665988.

It can be divided in two parts, 216 and 684, that added together give a square (900 = 30²).

The spelling of 216684 in words is "two hundred sixteen thousand, six hundred eighty-four".