18015661 has 2 divisors, whose sum is σ = 18015662. Its totient is φ = 18015660.

The previous prime is 18015649. The next prime is 18015677. The reversal of 18015661 is 16651081.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 9424900 + 8590761 = 3070^2 + 2931^2 .

It is a cyclic number.

It is not a de Polignac number, because 18015661 - 2⁷ = 18015533 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (18015761) 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, 9007830 + 9007831.

It is an arithmetic number, because the mean of its divisors is an integer number (9007831).

Almost surely, 2^18015661 is an apocalyptic number.

It is an amenable number.

18015661 is a deficient number, since it is larger than the sum of its proper divisors (1).

18015661 is an equidigital number, since it uses as much as digits as its factorization.

18015661 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 1440, while the sum is 28.

The square root of 18015661 is about 4244.4859523858. The cubic root of 18015661 is about 262.1501237419.

The spelling of 18015661 in words is "eighteen million, fifteen thousand, six hundred sixty-one".