666553 has 4 divisors (see below), whose sum is σ = 705780. Its totient is φ = 627328.

The previous prime is 666541. The next prime is 666557. The reversal of 666553 is 355666.

It is a happy number.

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 589824 + 76729 = 768^2 + 277^2 .

It is a cyclic number.

It is not a de Polignac number, because 666553 - 2⁹ = 666041 is a prime.

It is a Smith number, since the sum of its digits (31) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

It is a nialpdrome in base 10.

It is not an unprimeable number, because it can be changed into a prime (666557) 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 3 ways as a sum of consecutive naturals, for example, 19588 + ... + 19621.

It is an arithmetic number, because the mean of its divisors is an integer number (176445).

2⁶⁶⁶⁵⁵³ is an apocalyptic number.

It is an amenable number.

666553 is a deficient number, since it is larger than the sum of its proper divisors (39227).

666553 is a wasteful number, since it uses less digits than its factorization.

666553 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 39226.

The product of its digits is 16200, while the sum is 31.

The square root of 666553 is about 816.4269716270. The cubic root of 666553 is about 87.3530813425.

The spelling of 666553 in words is "six hundred sixty-six thousand, five hundred fifty-three".