166189561 has 4 divisors (see below), whose sum is σ = 174936400. Its totient is φ = 157442724.

The previous prime is 166189553. The next prime is 166189577. The reversal of 166189561 is 165981661.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also an emirpimes, since its reverse is a distinct semiprime: 165981661 = 5717 ⋅29033.

It is a cyclic number.

It is not a de Polignac number, because 166189561 - 2³ = 166189553 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (166189591) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 4373391 + ... + 4373428.

It is an arithmetic number, because the mean of its divisors is an integer number (43734100).

Almost surely, 2^166189561 is an apocalyptic number.

It is an amenable number.

166189561 is a deficient number, since it is larger than the sum of its proper divisors (8746839).

166189561 is an equidigital number, since it uses as much as digits as its factorization.

166189561 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 8746838.

The product of its digits is 77760, while the sum is 43.

The square root of 166189561 is about 12891.4530212851. The cubic root of 166189561 is about 549.7955835388.

The spelling of 166189561 in words is "one hundred sixty-six million, one hundred eighty-nine thousand, five hundred sixty-one".