666549217 has 4 divisors (see below), whose sum is σ = 670638640. Its totient is φ = 662459796.

The previous prime is 666549187. The next prime is 666549229. The reversal of 666549217 is 712945666.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-666549217 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (666549287) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2044467 + ... + 2044792.

It is an arithmetic number, because the mean of its divisors is an integer number (167659660).

Almost surely, 2^666549217 is an apocalyptic number.

It is an amenable number.

666549217 is a deficient number, since it is larger than the sum of its proper divisors (4089423).

666549217 is a wasteful number, since it uses less digits than its factorization.

666549217 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4089422.

The product of its digits is 544320, while the sum is 46.

The square root of 666549217 is about 25817.6144715192. The cubic root of 666549217 is about 873.5291608562.

The spelling of 666549217 in words is "six hundred sixty-six million, five hundred forty-nine thousand, two hundred seventeen".