166561561340544 has 128 divisors (see below), whose sum is σ = 444422709331200. Its totient is φ = 55270496927744.

The previous prime is 166561561340543. The next prime is 166561561340569. The reversal of 166561561340544 is 445043165165661.

It is a tau number, because it is divible by the number of its divisors (128).

It is not an unprimeable number, because it can be changed into a prime (166561561340543) 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, 287612044 + ... + 288190580.

It is an arithmetic number, because the mean of its divisors is an integer number (3472052416650).

Almost surely, 2^{166561561340544} is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 166561561340544, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (222211354665600).

166561561340544 is an abundant number, since it is smaller than the sum of its proper divisors (277861147990656).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

166561561340544 is a wasteful number, since it uses less digits than its factorization.

166561561340544 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 581930 (or 581918 counting only the distinct ones).

The product of its (nonzero) digits is 31104000, while the sum is 57.

The spelling of 166561561340544 in words is "one hundred sixty-six trillion, five hundred sixty-one billion, five hundred sixty-one million, three hundred forty thousand, five hundred forty-four".