666812009 has 4 divisors (see below), whose sum is σ = 673286016. Its totient is φ = 660338004.

The previous prime is 666811997. The next prime is 666812033. The reversal of 666812009 is 900218666.

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 not a de Polignac number, because 666812009 - 2¹⁶ = 666746473 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (666812059) 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, 3236849 + ... + 3237054.

It is an arithmetic number, because the mean of its divisors is an integer number (168321504).

Almost surely, 2^666812009 is an apocalyptic number.

It is an amenable number.

666812009 is a deficient number, since it is larger than the sum of its proper divisors (6474007).

666812009 is a wasteful number, since it uses less digits than its factorization.

666812009 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6474006.

The product of its (nonzero) digits is 31104, while the sum is 38.

The square root of 666812009 is about 25822.7033635133. The cubic root of 666812009 is about 873.6439442349.

The spelling of 666812009 in words is "six hundred sixty-six million, eight hundred twelve thousand, nine".