18543661 has 2 divisors, whose sum is σ = 18543662. Its totient is φ = 18543660.

The previous prime is 18543659. The next prime is 18543671. The reversal of 18543661 is 16634581.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 18541636 + 2025 = 4306^2 + 45^2 .

It is an emirp because it is prime and its reverse (16634581) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 18543661 - 2¹ = 18543659 is a prime.

Together with 18543659, 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 (18543671) 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, 9271830 + 9271831.

It is an arithmetic number, because the mean of its divisors is an integer number (9271831).

Almost surely, 2^18543661 is an apocalyptic number.

It is an amenable number.

18543661 is a deficient number, since it is larger than the sum of its proper divisors (1).

18543661 is an equidigital number, since it uses as much as digits as its factorization.

18543661 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 17280, while the sum is 34.

The square root of 18543661 is about 4306.2351305984. The cubic root of 18543661 is about 264.6865214530.

The spelling of 18543661 in words is "eighteen million, five hundred forty-three thousand, six hundred sixty-one".