18955681 has 2 divisors, whose sum is σ = 18955682. Its totient is φ = 18955680.

The previous prime is 18955661. The next prime is 18955687. The reversal of 18955681 is 18655981.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 15928081 + 3027600 = 3991^2 + 1740^2 .

It is an emirp because it is prime and its reverse (18655981) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 18955681 - 2⁹ = 18955169 is a prime.

It is a super-3 number, since 3×18955681³ (a number of 23 digits) contains 333 as substring. Note that it is a super-d number also for d = 2.

It is not a weakly prime, because it can be changed into another prime (18955687) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9477840 + 9477841.

It is an arithmetic number, because the mean of its divisors is an integer number (9477841).

Almost surely, 2^18955681 is an apocalyptic number.

It is an amenable number.

18955681 is a deficient number, since it is larger than the sum of its proper divisors (1).

18955681 is an equidigital number, since it uses as much as digits as its factorization.

18955681 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 86400, while the sum is 43.

The square root of 18955681 is about 4353.8122375684. The cubic root of 18955681 is about 266.6325280951.

The spelling of 18955681 in words is "eighteen million, nine hundred fifty-five thousand, six hundred eighty-one".