18216661 has 2 divisors, whose sum is σ = 18216662. Its totient is φ = 18216660.

The previous prime is 18216641. The next prime is 18216701. The reversal of 18216661 is 16661281.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 17892900 + 323761 = 4230^2 + 569^2 .

It is a cyclic number.

It is not a de Polignac number, because 18216661 - 2¹¹ = 18214613 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (18216641) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9108330 + 9108331.

It is an arithmetic number, because the mean of its divisors is an integer number (9108331).

Almost surely, 2^18216661 is an apocalyptic number.

It is an amenable number.

18216661 is a deficient number, since it is larger than the sum of its proper divisors (1).

18216661 is an equidigital number, since it uses as much as digits as its factorization.

18216661 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 3456, while the sum is 31.

The square root of 18216661 is about 4268.0980541689. The cubic root of 18216661 is about 263.1214530584.

The spelling of 18216661 in words is "eighteen million, two hundred sixteen thousand, six hundred sixty-one".