161581980881 has 4 divisors (see below), whose sum is σ = 161589161652. Its totient is φ = 161574800112.

The previous prime is 161581980841. The next prime is 161581980887. The reversal of 161581980881 is 188089185161.

161581980881 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 188089185161 = 7487 ⋅25122103.

It can be written as a sum of positive squares in 2 ways, for example, as 94405635025 + 67176345856 = 307255^2 + 259184^2 .

It is a cyclic number.

It is not a de Polignac number, because 161581980881 - 2²⁶ = 161514872017 is a prime.

It is a super-2 number, since 2×161581980881² (a number of 23 digits) contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (161581980887) 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 3 ways as a sum of consecutive naturals, for example, 3556526 + ... + 3601671.

It is an arithmetic number, because the mean of its divisors is an integer number (40397290413).

Almost surely, 2^161581980881 is an apocalyptic number.

It is an amenable number.

161581980881 is a deficient number, since it is larger than the sum of its proper divisors (7180771).

161581980881 is an equidigital number, since it uses as much as digits as its factorization.

161581980881 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7180770.

The product of its (nonzero) digits is 1105920, while the sum is 56.

The spelling of 161581980881 in words is "one hundred sixty-one billion, five hundred eighty-one million, nine hundred eighty thousand, eight hundred eighty-one".