166666661 has 16 divisors (see below), whose sum is σ = 193240320. Its totient is φ = 140797440.

The previous prime is 166666649. The next prime is 166666673.

166666661 is nontrivially palindromic in base 10.

It is an interprime number because it is at equal distance from previous prime (166666649) and next prime (166666673).

It is not a de Polignac number, because 166666661 - 2⁶ = 166666597 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (166666631) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 263816 + ... + 264446.

It is an arithmetic number, because the mean of its divisors is an integer number (12077520).

Almost surely, 2^166666661 is an apocalyptic number.

It is an amenable number.

166666661 is a deficient number, since it is larger than the sum of its proper divisors (26573659).

166666661 is an equidigital number, since it uses as much as digits as its factorization.

166666661 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1124.

The product of its digits is 279936, while the sum is 44.

The square root of 166666661 is about 12909.9442678890. The cubic root of 166666661 is about 550.3212019121.

The spelling of 166666661 in words is "one hundred sixty-six million, six hundred sixty-six thousand, six hundred sixty-one".