161605566661591 has 16 divisors (see below), whose sum is σ = 184462833358944. Its totient is φ = 140255701530624.

The previous prime is 161605566661549. The next prime is 161605566661619. The reversal of 161605566661591 is 195166665506161.

It is a happy number.

It is a cyclic number.

It is not a de Polignac number, because 161605566661591 - 2¹¹ = 161605566659543 is a prime.

It is a super-2 number, since 2×161605566661591² (a number of 29 digits) contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (161605566661531) 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, 374014845 + ... + 374446678.

It is an arithmetic number, because the mean of its divisors is an integer number (11528927084934).

Almost surely, 2^{161605566661591} is an apocalyptic number.

161605566661591 is a deficient number, since it is larger than the sum of its proper divisors (22857266697353).

161605566661591 is a wasteful number, since it uses less digits than its factorization.

161605566661591 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 748462530.

The product of its (nonzero) digits is 52488000, while the sum is 64.

The spelling of 161605566661591 in words is "one hundred sixty-one trillion, six hundred five billion, five hundred sixty-six million, six hundred sixty-one thousand, five hundred ninety-one".