18681643 has 2 divisors, whose sum is σ = 18681644. Its totient is φ = 18681642.

The previous prime is 18681613. The next prime is 18681647. The reversal of 18681643 is 34618681.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-18681643 is a prime.

It is not a weakly prime, because it can be changed into another prime (18681647) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9340821 + 9340822.

It is an arithmetic number, because the mean of its divisors is an integer number (9340822).

Almost surely, 2^18681643 is an apocalyptic number.

18681643 is a deficient number, since it is larger than the sum of its proper divisors (1).

18681643 is an equidigital number, since it uses as much as digits as its factorization.

18681643 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 27648, while the sum is 37.

The square root of 18681643 is about 4322.2266252477. The cubic root of 18681643 is about 265.3414040470.

The spelling of 18681643 in words is "eighteen million, six hundred eighty-one thousand, six hundred forty-three".