216820 has 24 divisors (see below), whose sum is σ = 469224. Its totient is φ = 84096.

The previous prime is 216803. The next prime is 216829. The reversal of 216820 is 28612.

It is a happy number.

It can be written as a sum of positive squares in 4 ways, for example, as 116964 + 99856 = 342^2 + 316^2 .

It is a plaindrome in base 11.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (216829) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 594 + ... + 886.

It is an arithmetic number, because the mean of its divisors is an integer number (19551).

2²¹⁶⁸²⁰ is an apocalyptic number.

216820 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 216820, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (234612).

216820 is an abundant number, since it is smaller than the sum of its proper divisors (252404).

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

216820 is a wasteful number, since it uses less digits than its factorization.

216820 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 339 (or 337 counting only the distinct ones).

The product of its (nonzero) digits is 192, while the sum is 19.

The square root of 216820 is about 465.6393454166. The cubic root of 216820 is about 60.0758300489.

The spelling of 216820 in words is "two hundred sixteen thousand, eight hundred twenty".