166666515809 has 4 divisors (see below), whose sum is σ = 168539173380. Its totient is φ = 164793858240.

The previous prime is 166666515803. The next prime is 166666515833. The reversal of 166666515809 is 908515666661.

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 115964086225 + 50702429584 = 340535^2 + 225172^2 .

It is a cyclic number.

It is not a de Polignac number, because 166666515809 - 2⁴ = 166666515793 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (166666515803) 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, 936328652 + ... + 936328829.

It is an arithmetic number, because the mean of its divisors is an integer number (42134793345).

Almost surely, 2^166666515809 is an apocalyptic number.

It is an amenable number.

166666515809 is a deficient number, since it is larger than the sum of its proper divisors (1872657571).

166666515809 is an equidigital number, since it uses as much as digits as its factorization.

166666515809 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1872657570.

The product of its (nonzero) digits is 13996800, while the sum is 59.

The spelling of 166666515809 in words is "one hundred sixty-six billion, six hundred sixty-six million, five hundred fifteen thousand, eight hundred nine".