166671561 has 16 divisors (see below), whose sum is σ = 254797184. Its totient is φ = 94932864.

The previous prime is 166671559. The next prime is 166671563. The reversal of 166671561 is 165176661.

It is an interprime number because it is at equal distance from previous prime (166671559) and next prime (166671563).

It is not a de Polignac number, because 166671561 - 2¹ = 166671559 is a prime.

It is a Smith number, since the sum of its digits (39) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (166671563) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 6106 + ... + 19251.

It is an arithmetic number, because the mean of its divisors is an integer number (15924824).

Almost surely, 2^166671561 is an apocalyptic number.

It is an amenable number.

166671561 is a deficient number, since it is larger than the sum of its proper divisors (88125623).

166671561 is a wasteful number, since it uses less digits than its factorization.

166671561 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 25680.

The product of its digits is 45360, while the sum is 39.

The square root of 166671561 is about 12910.1340426814. The cubic root of 166671561 is about 550.3265950072.

The spelling of 166671561 in words is "one hundred sixty-six million, six hundred seventy-one thousand, five hundred sixty-one".