216999 has 24 divisors (see below), whose sum is σ = 349440. Its totient is φ = 134136.

The previous prime is 216991. The next prime is 217001. The reversal of 216999 is 999612.

It is not a de Polignac number, because 216999 - 2³ = 216991 is a prime.

It is a Smith number, since the sum of its digits (36) coincides with the sum of the digits of its prime factors.

Its product of digits (8748) is a multiple of the sum of its prime factors (81).

216999 is a modest number, since divided by 999 gives 216 as remainder.

It is a plaindrome in base 15.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (216991) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 4594 + ... + 4640.

It is an arithmetic number, because the mean of its divisors is an integer number (14560).

2²¹⁶⁹⁹⁹ is an apocalyptic number.

216999 is a deficient number, since it is larger than the sum of its proper divisors (132441).

216999 is an equidigital number, since it uses as much as digits as its factorization.

216999 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 81 (or 69 counting only the distinct ones).

The product of its digits is 8748, while the sum is 36.

The square root of 216999 is about 465.8315146059. The cubic root of 216999 is about 60.0923577611.

The spelling of 216999 in words is "two hundred sixteen thousand, nine hundred ninety-nine".