18616681 has 2 divisors, whose sum is σ = 18616682. Its totient is φ = 18616680.

The previous prime is 18616669. The next prime is 18616693. The reversal of 18616681 is 18661681.

It is a happy number.

It is a balanced prime because it is at equal distance from previous prime (18616669) and next prime (18616693).

It can be written as a sum of positive squares in only one way, i.e., 18275625 + 341056 = 4275^2 + 584^2 .

It is an emirp because it is prime and its reverse (18661681) is a distict prime. It is also a bemirp because it and its reverse can be mirrored producing other two distinct primes, 18991981 and 18919981.

It is a cyclic number.

It is not a de Polignac number, because 18616681 - 2¹¹ = 18614633 is a prime.

It is a super-2 number, since 2×18616681² = 693161622911522, which contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 18616681.

It is not a weakly prime, because it can be changed into another prime (18616601) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9308340 + 9308341.

It is an arithmetic number, because the mean of its divisors is an integer number (9308341).

Almost surely, 2^18616681 is an apocalyptic number.

It is an amenable number.

18616681 is a deficient number, since it is larger than the sum of its proper divisors (1).

18616681 is an equidigital number, since it uses as much as digits as its factorization.

18616681 is an evil number, because the sum of its binary digits is even.

The product of its digits is 13824, while the sum is 37.

The square root of 18616681 is about 4314.7052042984. The cubic root of 18616681 is about 265.0334881140.

The spelling of 18616681 in words is "eighteen million, six hundred sixteen thousand, six hundred eighty-one".