161818281 has 6 divisors (see below), whose sum is σ = 233737530. Its totient is φ = 107878848.

The previous prime is 161818277. The next prime is 161818303. The reversal of 161818281 is 182818161.

It is a happy number.

161818281 is a `hidden beast` number, since 1 + 618 + 18 + 28 + 1 = 666.

It can be written as a sum of positive squares in only one way, i.e., 161798400 + 19881 = 12720^2 + 141^2 .

It is not a de Polignac number, because 161818281 - 2² = 161818277 is a prime.

It is a super-2 number, since 2×161818281² = 52370312131589922, which contains 22 as substring.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (161818201) 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 5 ways as a sum of consecutive naturals, for example, 8989896 + ... + 8989913.

It is an arithmetic number, because the mean of its divisors is an integer number (38956255).

Almost surely, 2^161818281 is an apocalyptic number.

It is an amenable number.

161818281 is a deficient number, since it is larger than the sum of its proper divisors (71919249).

161818281 is a wasteful number, since it uses less digits than its factorization.

161818281 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 17979815 (or 17979812 counting only the distinct ones).

The product of its digits is 6144, while the sum is 36.

The square root of 161818281 is about 12720.7814618442. The cubic root of 161818281 is about 544.9322711335.

The spelling of 161818281 in words is "one hundred sixty-one million, eight hundred eighteen thousand, two hundred eighty-one".