217989 has 12 divisors (see below), whose sum is σ = 321516. Its totient is φ = 142272.

The previous prime is 217981. The next prime is 218003. The reversal of 217989 is 989712.

It is a happy number.

217989 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It can be written as a sum of positive squares in 2 ways, for example, as 173889 + 44100 = 417^2 + 210^2 .

It is not a de Polignac number, because 217989 - 2³ = 217981 is a prime.

217989 is a lucky number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (217981) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 249 + ... + 705.

It is an arithmetic number, because the mean of its divisors is an integer number (26793).

2²¹⁷⁹⁸⁹ is an apocalyptic number.

It is an amenable number.

217989 is a deficient number, since it is larger than the sum of its proper divisors (103527).

217989 is a wasteful number, since it uses less digits than its factorization.

217989 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 516 (or 513 counting only the distinct ones).

The product of its digits is 9072, while the sum is 36.

The square root of 217989 is about 466.8929213428. The cubic root of 217989 is about 60.1836042516.

The spelling of 217989 in words is "two hundred seventeen thousand, nine hundred eighty-nine".