666813 has 16 divisors (see below), whose sum is σ = 1028736. Its totient is φ = 376320.

The previous prime is 666811. The next prime is 666821. The reversal of 666813 is 318666.

It is not a de Polignac number, because 666813 - 2¹ = 666811 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (666811) 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 15 ways as a sum of consecutive naturals, for example, 2233 + ... + 2513.

It is an arithmetic number, because the mean of its divisors is an integer number (64296).

2⁶⁶⁶⁸¹³ is an apocalyptic number.

It is an amenable number.

666813 is a deficient number, since it is larger than the sum of its proper divisors (361923).

666813 is a wasteful number, since it uses less digits than its factorization.

666813 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 404.

The product of its digits is 5184, while the sum is 30.

The square root of 666813 is about 816.5861865106. The cubic root of 666813 is about 87.3644377031.

The spelling of 666813 in words is "six hundred sixty-six thousand, eight hundred thirteen".