161656161 has 24 divisors (see below), whose sum is σ = 231306624. Its totient is φ = 100383840.

The previous prime is 161656147. The next prime is 161656163.

161656161 is nontrivially palindromic in base 10.

It is not a de Polignac number, because 161656161 - 2¹⁸ = 161394017 is a prime.

It is a super-2 number, since 2×161656161² = 52265428778515842, which contains 22 as substring.

It is an alternating number because its digits alternate between odd and even.

It is not an unprimeable number, because it can be changed into a prime (161656163) 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 23 ways as a sum of consecutive naturals, for example, 64840 + ... + 67286.

It is an arithmetic number, because the mean of its divisors is an integer number (9637776).

Almost surely, 2^161656161 is an apocalyptic number.

161656161 is the 7341-st octagonal number.

It is an amenable number.

161656161 is a deficient number, since it is larger than the sum of its proper divisors (69650463).

161656161 is a wasteful number, since it uses less digits than its factorization.

161656161 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2549 (or 2530 counting only the distinct ones).

The product of its digits is 6480, while the sum is 33.

The square root of 161656161 is about 12714.4076149855. The cubic root of 161656161 is about 544.7502275499.

The spelling of 161656161 in words is "one hundred sixty-one million, six hundred fifty-six thousand, one hundred sixty-one".