666001 has 4 divisors (see below), whose sum is σ = 761152. Its totient is φ = 570852.

The previous prime is 665993. The next prime is 666013. The reversal of 666001 is 100666.

It is a happy number.

666001 is nontrivially palindromic in base 3.

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: 100666 = 2 ⋅50333.

It is a cyclic number.

It is not a de Polignac number, because 666001 - 2³ = 665993 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 666001.

It is not an unprimeable number, because it can be changed into a prime (666031) 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, 47565 + ... + 47578.

It is an arithmetic number, because the mean of its divisors is an integer number (190288).

2⁶⁶⁶⁰⁰¹ is an apocalyptic number.

It is an amenable number.

666001 is a deficient number, since it is larger than the sum of its proper divisors (95151).

666001 is an equidigital number, since it uses as much as digits as its factorization.

666001 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 95150.

The product of its (nonzero) digits is 216, while the sum is 19.

The square root of 666001 is about 816.0888432027. The cubic root of 666001 is about 87.3289611211.

Adding to 666001 its reverse (100666), we get a palindrome (766667).

The spelling of 666001 in words is "six hundred sixty-six thousand, one".