166609959391 has 4 divisors (see below), whose sum is σ = 170154852192. Its totient is φ = 163065066592.

The previous prime is 166609959343. The next prime is 166609959401. The reversal of 166609959391 is 193959906661.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 193959906661 = 61 ⋅3179670601.

It is a cyclic number.

It is not a de Polignac number, because 166609959391 - 2²⁹ = 166073088479 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (166609959311) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1772446330 + ... + 1772446423.

It is an arithmetic number, because the mean of its divisors is an integer number (42538713048).

Almost surely, 2^166609959391 is an apocalyptic number.

166609959391 is a deficient number, since it is larger than the sum of its proper divisors (3544892801).

166609959391 is an equidigital number, since it uses as much as digits as its factorization.

166609959391 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3544892800.

The product of its (nonzero) digits is 21257640, while the sum is 64.

The spelling of 166609959391 in words is "one hundred sixty-six billion, six hundred nine million, nine hundred fifty-nine thousand, three hundred ninety-one".