161156681 has 4 divisors (see below), whose sum is σ = 184179072. Its totient is φ = 138134292.

The previous prime is 161156657. The next prime is 161156717. The reversal of 161156681 is 186651161.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also an emirpimes, since its reverse is a distinct semiprime: 186651161 = 59 ⋅3163579.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-161156681 is a prime.

It is a super-2 number, since 2×161156681² = 51942951661871522, which contains 22 as substring.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (161156621) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 11511185 + ... + 11511198.

It is an arithmetic number, because the mean of its divisors is an integer number (46044768).

Almost surely, 2^161156681 is an apocalyptic number.

It is an amenable number.

161156681 is a deficient number, since it is larger than the sum of its proper divisors (23022391).

161156681 is an equidigital number, since it uses as much as digits as its factorization.

161156681 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 23022390.

The product of its digits is 8640, while the sum is 35.

The square root of 161156681 is about 12694.7501353906. The cubic root of 161156681 is about 544.1885981476.

The spelling of 161156681 in words is "one hundred sixty-one million, one hundred fifty-six thousand, six hundred eighty-one".