216640 has 28 divisors (see below), whose sum is σ = 516636. Its totient is φ = 86528.

The previous prime is 216617. The next prime is 216641. The reversal of 216640 is 46612.

It can be written as a sum of positive squares in 2 ways, for example, as 166464 + 50176 = 408^2 + 224^2 .

It is not an unprimeable number, because it can be changed into a prime (216641) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 19 + ... + 658.

2²¹⁶⁶⁴⁰ is an apocalyptic number.

216640 is a gapful number since it is divisible by the number (20) 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 216640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (258318).

216640 is an abundant number, since it is smaller than the sum of its proper divisors (299996).

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

216640 is an equidigital number, since it uses as much as digits as its factorization.

216640 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 694 (or 684 counting only the distinct ones).

The product of its (nonzero) digits is 288, while the sum is 19.

The square root of 216640 is about 465.4460226492. The cubic root of 216640 is about 60.0592008277.

The spelling of 216640 in words is "two hundred sixteen thousand, six hundred forty".