667809 has 6 divisors (see below), whose sum is σ = 964626. Its totient is φ = 445200.

The previous prime is 667801. The next prime is 667817. The reversal of 667809 is 908766.

It is an interprime number because it is at equal distance from previous prime (667801) and next prime (667817).

It can be written as a sum of positive squares in only one way, i.e., 451584 + 216225 = 672^2 + 465^2 .

It is not a de Polignac number, because 667809 - 2³ = 667801 is a prime.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (667801) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 37092 + ... + 37109.

It is an arithmetic number, because the mean of its divisors is an integer number (160771).

2⁶⁶⁷⁸⁰⁹ is an apocalyptic number.

It is an amenable number.

667809 is a deficient number, since it is larger than the sum of its proper divisors (296817).

667809 is a wasteful number, since it uses less digits than its factorization.

667809 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 74207 (or 74204 counting only the distinct ones).

The product of its (nonzero) digits is 18144, while the sum is 36.

The square root of 667809 is about 817.1958149673. The cubic root of 667809 is about 87.4079140060.

It can be divided in two parts, 66 and 7809, that added together give a triangular number (7875 = T₁₂₅).

The spelling of 667809 in words is "six hundred sixty-seven thousand, eight hundred nine".