666217 has 4 divisors (see below), whose sum is σ = 689220. Its totient is φ = 643216.

The previous prime is 666203. The next prime is 666229. The reversal of 666217 is 712666.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 712666 = 2 ⋅356333.

It can be written as a sum of positive squares in 2 ways, for example, as 364816 + 301401 = 604^2 + 549^2 .

It is a cyclic number.

It is not a de Polignac number, because 666217 - 2⁷ = 666089 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (666277) 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, 11458 + ... + 11515.

It is an arithmetic number, because the mean of its divisors is an integer number (172305).

2⁶⁶⁶²¹⁷ is an apocalyptic number.

It is an amenable number.

666217 is a deficient number, since it is larger than the sum of its proper divisors (23003).

666217 is a wasteful number, since it uses less digits than its factorization.

666217 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 23002.

The product of its digits is 3024, while the sum is 28.

The square root of 666217 is about 816.2211710070. The cubic root of 666217 is about 87.3384010552.

The spelling of 666217 in words is "six hundred sixty-six thousand, two hundred seventeen".