166566561505 has 4 divisors (see below), whose sum is σ = 199879873812. Its totient is φ = 133253249200.

The previous prime is 166566561479. The next prime is 166566561517. The reversal of 166566561505 is 505165665661.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 89779934689 + 76786626816 = 299633^2 + 277104^2 .

It is a de Polignac number, because none of the positive numbers 2^k-166566561505 is a prime.

It is a Duffinian number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 16656656146 + ... + 16656656155.

It is an arithmetic number, because the mean of its divisors is an integer number (49969968453).

Almost surely, 2^166566561505 is an apocalyptic number.

It is an amenable number.

166566561505 is a deficient number, since it is larger than the sum of its proper divisors (33313312307).

166566561505 is an equidigital number, since it uses as much as digits as its factorization.

166566561505 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 33313312306.

The product of its (nonzero) digits is 4860000, while the sum is 52.

The spelling of 166566561505 in words is "one hundred sixty-six billion, five hundred sixty-six million, five hundred sixty-one thousand, five hundred five".