161605566661661 has 2 divisors, whose sum is σ = 161605566661662. Its totient is φ = 161605566661660.

The previous prime is 161605566661631. The next prime is 161605566661667. The reversal of 161605566661661 is 166166665506161.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 109005084302500 + 52600482359161 = 10440550^2 + 7252619^2 .

It is a cyclic number.

It is not a de Polignac number, because 161605566661661 - 2³⁴ = 161588386792477 is a prime.

It is a super-2 number, since 2×161605566661661² (a number of 29 digits) contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 161605566661594 and 161605566661603.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (161605566661667) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 80802783330830 + 80802783330831.

It is an arithmetic number, because the mean of its divisors is an integer number (80802783330831).

Almost surely, 2^{161605566661661} is an apocalyptic number.

It is an amenable number.

161605566661661 is a deficient number, since it is larger than the sum of its proper divisors (1).

161605566661661 is an equidigital number, since it uses as much as digits as its factorization.

161605566661661 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 41990400, while the sum is 62.

The spelling of 161605566661661 in words is "one hundred sixty-one trillion, six hundred five billion, five hundred sixty-six million, six hundred sixty-one thousand, six hundred sixty-one".