166601506605665 has 4 divisors (see below), whose sum is σ = 199921807926804. Its totient is φ = 133281205284528.

The previous prime is 166601506605659. The next prime is 166601506605727. The reversal of 166601506605665 is 566506605106661.

It is a happy number.

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 45773573390689 + 120827933214976 = 6765617^2 + 10992176^2 .

It is a cyclic number.

It is not a de Polignac number, because 166601506605665 - 2⁴⁴ = 149009320561249 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 16660150660562 + ... + 16660150660571.

It is an arithmetic number, because the mean of its divisors is an integer number (49980451981701).

Almost surely, 2^{166601506605665} is an apocalyptic number.

It is an amenable number.

166601506605665 is a deficient number, since it is larger than the sum of its proper divisors (33320301321139).

166601506605665 is an equidigital number, since it uses as much as digits as its factorization.

166601506605665 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 33320301321138.

The product of its (nonzero) digits is 34992000, while the sum is 59.

The spelling of 166601506605665 in words is "one hundred sixty-six trillion, six hundred one billion, five hundred six million, six hundred five thousand, six hundred sixty-five".