666666 has 96 divisors (see below), whose sum is σ = 1991808. Its totient is φ = 155520.

The previous prime is 666649. The next prime is 666667.

666666 is nontrivially palindromic in base 10 and base 16.

It is a nude number because it is divisible by every one of its digits.

666666 is a modest number, since divided by 6666 gives 66 as remainder.

666666 is a nontrivial repdigit in base 10.

It is a plaindrome in base 10.

It is a nialpdrome in base 7 and base 10.

It is a zygodrome in base 10.

It is a self number, because there is not a number n which added to its sum of digits gives 666666.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (666667) by changing a digit.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 18000 + ... + 18036.

It is an arithmetic number, because the mean of its divisors is an integer number (20748).

It is a self-describing number.

2⁶⁶⁶⁶⁶⁶ is an apocalyptic number.

666666 is a gapful number since it is divisible by the number (66) formed by its first and last digit.

It is a practical number, because each smaller number is the sum of distinct divisors of 666666, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (995904).

666666 is an abundant number, since it is smaller than the sum of its proper divisors (1325142).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

666666 is a wasteful number, since it uses less digits than its factorization.

666666 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 76 (or 73 counting only the distinct ones).

The product of its digits is 46656, while the sum is 36.

The square root of 666666 is about 816.4961726793. The cubic root of 666666 is about 87.3580173543.

The spelling of 666666 in words is "six hundred sixty-six thousand, six hundred sixty-six".