666566 has 4 divisors (see below), whose sum is σ = 999852. Its totient is φ = 333282.

The previous prime is 666559. The next prime is 666599. The reversal of 666566 is 665666.

666566 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.

It is a Curzon number.

It is a congruent number.

It is an unprimeable number.

666566 is an untouchable number, because it is not equal to the sum of proper divisors of any number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 166640 + ... + 166643.

It is an arithmetic number, because the mean of its divisors is an integer number (249963).

2⁶⁶⁶⁵⁶⁶ is an apocalyptic number.

666566 is a deficient number, since it is larger than the sum of its proper divisors (333286).

666566 is a wasteful number, since it uses less digits than its factorization.

666566 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 333285.

The product of its digits is 38880, while the sum is 35.

The square root of 666566 is about 816.4349331086. The cubic root of 666566 is about 87.3536492306.

Subtracting from 666566 its reverse (665666), we obtain a square (900 = 30²).

The spelling of 666566 in words is "six hundred sixty-six thousand, five hundred sixty-six".