166561660665 has 64 divisors (see below), whose sum is σ = 315816952320. Its totient is φ = 82996992000.

The previous prime is 166561660663. The next prime is 166561660669. The reversal of 166561660665 is 566066165661.

166561660665 is a `hidden beast` number, since 16 + 6 + 5 + 6 + 16 + 606 + 6 + 5 = 666.

It is not a de Polignac number, because 166561660665 - 2¹ = 166561660663 is a prime.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (166561660663) by changing a digit.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 49540 + ... + 579290.

It is an arithmetic number, because the mean of its divisors is an integer number (4934639880).

Almost surely, 2^166561660665 is an apocalyptic number.

166561660665 is a gapful number since it is divisible by the number (15) formed by its first and last digit.

It is an amenable number.

166561660665 is a deficient number, since it is larger than the sum of its proper divisors (149255291655).

166561660665 is a wasteful number, since it uses less digits than its factorization.

166561660665 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 529919 (or 529913 counting only the distinct ones).

The product of its (nonzero) digits is 6998400, while the sum is 54.

The spelling of 166561660665 in words is "one hundred sixty-six billion, five hundred sixty-one million, six hundred sixty thousand, six hundred sixty-five".