666549 has 24 divisors (see below), whose sum is σ = 1080352. Its totient is φ = 408240.

The previous prime is 666541. The next prime is 666557. The reversal of 666549 is 945666.

It is a happy number.

It is an interprime number because it is at equal distance from previous prime (666541) and next prime (666557).

It is not a de Polignac number, because 666549 - 2³ = 666541 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (666541) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 3054 + ... + 3264.

2⁶⁶⁶⁵⁴⁹ is an apocalyptic number.

It is an amenable number.

666549 is a deficient number, since it is larger than the sum of its proper divisors (413803).

666549 is a wasteful number, since it uses less digits than its factorization.

666549 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 239 (or 227 counting only the distinct ones).

The product of its digits is 38880, while the sum is 36.

The square root of 666549 is about 816.4245219247. The cubic root of 666549 is about 87.3529066062.

It can be divided in two parts, 66 and 6549, that multiplied together give a palindrome (432234).

The spelling of 666549 in words is "six hundred sixty-six thousand, five hundred forty-nine".