1666843509185 has 4 divisors (see below), whose sum is σ = 2000212211028. Its totient is φ = 1333474807344.

The previous prime is 1666843509157. The next prime is 1666843509187. The reversal of 1666843509185 is 5819053486661.

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 823912028416 + 842931480769 = 907696^2 + 918113^2 .

It is a cyclic number.

It is not a de Polignac number, because 1666843509185 - 2³⁸ = 1391965602241 is a prime.

It is a super-2 number, since 2×1666843509185² (a number of 25 digits) contains 22 as substring.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (1666843509187) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 166684350914 + ... + 166684350923.

It is an arithmetic number, because the mean of its divisors is an integer number (500053052757).

Almost surely, 2^{1666843509185} is an apocalyptic number.

It is an amenable number.

1666843509185 is a deficient number, since it is larger than the sum of its proper divisors (333368701843).

1666843509185 is an equidigital number, since it uses as much as digits as its factorization.

1666843509185 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 333368701842.

The product of its (nonzero) digits is 37324800, while the sum is 62.

The spelling of 1666843509185 in words is "one trillion, six hundred sixty-six billion, eight hundred forty-three million, five hundred nine thousand, one hundred eighty-five".