18865661 has 2 divisors, whose sum is σ = 18865662. Its totient is φ = 18865660.

The previous prime is 18865619. The next prime is 18865669. The reversal of 18865661 is 16656881.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 16080100 + 2785561 = 4010^2 + 1669^2 .

It is an emirp because it is prime and its reverse (16656881) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 18865661 - 2¹⁸ = 18603517 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (18865669) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9432830 + 9432831.

It is an arithmetic number, because the mean of its divisors is an integer number (9432831).

Almost surely, 2^18865661 is an apocalyptic number.

It is an amenable number.

18865661 is a deficient number, since it is larger than the sum of its proper divisors (1).

18865661 is an equidigital number, since it uses as much as digits as its factorization.

18865661 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 69120, while the sum is 41.

The square root of 18865661 is about 4343.4618681416. The cubic root of 18865661 is about 266.2097813717.

The spelling of 18865661 in words is "eighteen million, eight hundred sixty-five thousand, six hundred sixty-one".