666667409 has 4 divisors (see below), whose sum is σ = 666758640. Its totient is φ = 666576180.

The previous prime is 666667403. The next prime is 666667433. The reversal of 666667409 is 904766666.

It is a happy number.

666667409 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

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, and also an emirpimes, since its reverse is a distinct semiprime: 904766666 = 2 ⋅452383333.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-666667409 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (666667403) 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, 33599 + ... + 49620.

It is an arithmetic number, because the mean of its divisors is an integer number (166689660).

Almost surely, 2^666667409 is an apocalyptic number.

It is an amenable number.

666667409 is a deficient number, since it is larger than the sum of its proper divisors (91231).

666667409 is an equidigital number, since it uses as much as digits as its factorization.

666667409 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 91230.

The product of its (nonzero) digits is 1959552, while the sum is 50.

The square root of 666667409 is about 25819.9033499353. The cubic root of 666667409 is about 873.5807889801.

The spelling of 666667409 in words is "six hundred sixty-six million, six hundred sixty-seven thousand, four hundred nine".