18109681 has 2 divisors, whose sum is σ = 18109682. Its totient is φ = 18109680.

The previous prime is 18109667. The next prime is 18109691. The reversal of 18109681 is 18690181.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 10497600 + 7612081 = 3240^2 + 2759^2 .

It is a cyclic number.

It is not a de Polignac number, because 18109681 - 2¹⁵ = 18076913 is a prime.

It is a super-2 number, since 2×18109681² = 655921091843522, which contains 22 as substring.

It is equal to p_1157866 and since 18109681 and 1157866 have the same sum of digits, it is a Honaker prime.

It is not a weakly prime, because it can be changed into another prime (18109661) 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, 9054840 + 9054841.

It is an arithmetic number, because the mean of its divisors is an integer number (9054841).

Almost surely, 2^18109681 is an apocalyptic number.

It is an amenable number.

18109681 is a deficient number, since it is larger than the sum of its proper divisors (1).

18109681 is an equidigital number, since it uses as much as digits as its factorization.

18109681 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 3456, while the sum is 34.

The square root of 18109681 is about 4255.5470858633. The cubic root of 18109681 is about 262.6053684323.

The spelling of 18109681 in words is "eighteen million, one hundred nine thousand, six hundred eighty-one".