181616321 has 16 divisors (see below), whose sum is σ = 199438848. Its totient is φ = 164640000.

The previous prime is 181616317. The next prime is 181616327. The reversal of 181616321 is 123616181.

It is a cyclic number.

It is not a de Polignac number, because 181616321 - 2² = 181616317 is a prime.

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

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (181616327) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 131591 + ... + 132963.

It is an arithmetic number, because the mean of its divisors is an integer number (12464928).

Almost surely, 2^181616321 is an apocalyptic number.

181616321 is the 7781-st octagonal number.

It is an amenable number.

181616321 is a deficient number, since it is larger than the sum of its proper divisors (17822527).

181616321 is a wasteful number, since it uses less digits than its factorization.

181616321 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1672.

The product of its digits is 1728, while the sum is 29.

The square root of 181616321 is about 13476.5099710570. The cubic root of 181616321 is about 566.3066019793.

The spelling of 181616321 in words is "one hundred eighty-one million, six hundred sixteen thousand, three hundred twenty-one".