18009661 has 2 divisors, whose sum is σ = 18009662. Its totient is φ = 18009660.

The previous prime is 18009659. The next prime is 18009679. The reversal of 18009661 is 16690081.

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., 17690436 + 319225 = 4206^2 + 565^2 .

It is a cyclic number.

It is not a de Polignac number, because 18009661 - 2¹ = 18009659 is a prime.

Together with 18009659, 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 (18009631) 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, 9004830 + 9004831.

It is an arithmetic number, because the mean of its divisors is an integer number (9004831).

Almost surely, 2^18009661 is an apocalyptic number.

It is an amenable number.

18009661 is a deficient number, since it is larger than the sum of its proper divisors (1).

18009661 is an equidigital number, since it uses as much as digits as its factorization.

18009661 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 2592, while the sum is 31.

The square root of 18009661 is about 4243.7790941565. The cubic root of 18009661 is about 262.1210180398.

The spelling of 18009661 in words is "eighteen million, nine thousand, six hundred sixty-one".