181855813 has 2 divisors, whose sum is σ = 181855814. Its totient is φ = 181855812.

The previous prime is 181855811. The next prime is 181855847. The reversal of 181855813 is 318558181.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 181521729 + 334084 = 13473^2 + 578^2 .

It is a cyclic number.

It is not a de Polignac number, because 181855813 - 2¹ = 181855811 is a prime.

Together with 181855811, it forms a pair of twin primes.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (181855811) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 90927906 + 90927907.

It is an arithmetic number, because the mean of its divisors is an integer number (90927907).

Almost surely, 2^181855813 is an apocalyptic number.

It is an amenable number.

181855813 is a deficient number, since it is larger than the sum of its proper divisors (1).

181855813 is an equidigital number, since it uses as much as digits as its factorization.

181855813 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 38400, while the sum is 40.

The square root of 181855813 is about 13485.3925786386. The cubic root of 181855813 is about 566.5554164918. Note that the first 3 decimals are identical.

The spelling of 181855813 in words is "one hundred eighty-one million, eight hundred fifty-five thousand, eight hundred thirteen".