666605 has 4 divisors (see below), whose sum is σ = 799932. Its totient is φ = 533280.

The previous prime is 666599. The next prime is 666607. The reversal of 666605 is 506666.

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 434281 + 232324 = 659^2 + 482^2 .

It is not a de Polignac number, because 666605 - 2⁶ = 666541 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (666607) 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, 66656 + ... + 66665.

It is an arithmetic number, because the mean of its divisors is an integer number (199983).

2⁶⁶⁶⁶⁰⁵ is an apocalyptic number.

It is an amenable number.

666605 is a deficient number, since it is larger than the sum of its proper divisors (133327).

666605 is a wasteful number, since it uses less digits than its factorization.

666605 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 133326.

The product of its (nonzero) digits is 6480, while the sum is 29.

The square root of 666605 is about 816.4588170875. The cubic root of 666605 is about 87.3553528508.

The spelling of 666605 in words is "six hundred sixty-six thousand, six hundred five".