166011561 has 24 divisors (see below), whose sum is σ = 247216320. Its totient is φ = 107301600.

The previous prime is 166011557. The next prime is 166011623. The reversal of 166011561 is 165110661.

166011561 is a `hidden beast` number, since 1 + 6 + 601 + 1 + 56 + 1 = 666.

It is not a de Polignac number, because 166011561 - 2² = 166011557 is a prime.

It is not an unprimeable number, because it can be changed into a prime (166021561) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 36850 + ... + 41108.

It is an arithmetic number, because the mean of its divisors is an integer number (10300680).

Almost surely, 2^166011561 is an apocalyptic number.

It is an amenable number.

166011561 is a deficient number, since it is larger than the sum of its proper divisors (81204759).

166011561 is a wasteful number, since it uses less digits than its factorization.

166011561 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4397 (or 4394 counting only the distinct ones).

The product of its (nonzero) digits is 1080, while the sum is 27.

The square root of 166011561 is about 12884.5473727252. The cubic root of 166011561 is about 549.5992242859.

The spelling of 166011561 in words is "one hundred sixty-six million, eleven thousand, five hundred sixty-one".