217985 has 4 divisors (see below), whose sum is σ = 261588. Its totient is φ = 174384.

The previous prime is 217981. The next prime is 218003. The reversal of 217985 is 589712.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 27889 + 190096 = 167^2 + 436^2 .

It is a cyclic number.

It is not a de Polignac number, because 217985 - 2² = 217981 is a prime.

It is a Duffinian 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 3 ways as a sum of consecutive naturals, for example, 21794 + ... + 21803.

It is an arithmetic number, because the mean of its divisors is an integer number (65397).

2²¹⁷⁹⁸⁵ is an apocalyptic number.

It is an amenable number.

217985 is a deficient number, since it is larger than the sum of its proper divisors (43603).

217985 is an equidigital number, since it uses as much as digits as its factorization.

217985 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 43602.

The product of its digits is 5040, while the sum is 32.

The square root of 217985 is about 466.8886376857. Note that the first 3 decimals coincide. The cubic root of 217985 is about 60.1832361353.

The spelling of 217985 in words is "two hundred seventeen thousand, nine hundred eighty-five".