18156661 has 2 divisors, whose sum is σ = 18156662. Its totient is φ = 18156660.

The previous prime is 18156659. The next prime is 18156673. The reversal of 18156661 is 16665181.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 14938225 + 3218436 = 3865^2 + 1794^2 .

It is a cyclic number.

It is not a de Polignac number, because 18156661 - 2¹ = 18156659 is a prime.

Together with 18156659, 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 (18156631) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9078330 + 9078331.

It is an arithmetic number, because the mean of its divisors is an integer number (9078331).

Almost surely, 2^18156661 is an apocalyptic number.

It is an amenable number.

18156661 is a deficient number, since it is larger than the sum of its proper divisors (1).

18156661 is an equidigital number, since it uses as much as digits as its factorization.

18156661 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 8640, while the sum is 34.

The square root of 18156661 is about 4261.0633649360. The cubic root of 18156661 is about 262.8322553148.

The spelling of 18156661 in words is "eighteen million, one hundred fifty-six thousand, six hundred sixty-one".