166561118161 has 9 divisors (see below), whose sum is σ = 176942537499. Its totient is φ = 156756875424.

The previous prime is 166561118153. The next prime is 166561118167. The reversal of 166561118161 is 161811165661.

It is a happy number.

The square root of 166561118161 is 408119.

It is a perfect power (a square), and thus also a powerful number.

It can be written as a sum of positive squares in only one way, i.e., 129675611025 + 36885507136 = 360105^2 + 192056^2 .

It is not a de Polignac number, because 166561118161 - 2³ = 166561118153 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (166561118167) by changing a digit.

It is a polite number, since it can be written in 8 ways as a sum of consecutive naturals, for example, 6926020 + ... + 6950026.

Almost surely, 2^166561118161 is an apocalyptic number.

166561118161 is the 408119-th square number.

166561118161 is the 204060-th centered octagonal number.

It is an amenable number.

166561118161 is a deficient number, since it is larger than the sum of its proper divisors (10381419338).

166561118161 is an frugal number, since it uses more digits than its factorization.

166561118161 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 48048 (or 24024 counting only the distinct ones).

The product of its digits is 51840, while the sum is 43.

The spelling of 166561118161 in words is "one hundred sixty-six billion, five hundred sixty-one million, one hundred eighteen thousand, one hundred sixty-one".