165661243561 has 16 divisors (see below), whose sum is σ = 201423188160. Its totient is φ = 134282119680.

The previous prime is 165661243529. The next prime is 165661243591. The reversal of 165661243561 is 165342166561.

It is a happy number.

165661243561 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a cyclic number.

It is not a de Polignac number, because 165661243561 - 2⁵ = 165661243529 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (165661243591) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 23309316 + ... + 23316421.

It is an arithmetic number, because the mean of its divisors is an integer number (12588949260).

Almost surely, 2^165661243561 is an apocalyptic number.

165661243561 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

It is an amenable number.

165661243561 is a deficient number, since it is larger than the sum of its proper divisors (35761944599).

165661243561 is a wasteful number, since it uses less digits than its factorization.

165661243561 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 46625784.

The product of its digits is 777600, while the sum is 46.

The spelling of 165661243561 in words is "one hundred sixty-five billion, six hundred sixty-one million, two hundred forty-three thousand, five hundred sixty-one".