18165661 has 4 divisors (see below), whose sum is σ = 18181024. Its totient is φ = 18150300.

The previous prime is 18165647. The next prime is 18165683. The reversal of 18165661 is 16656181.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also an emirpimes, since its reverse is a distinct semiprime: 16656181 = 109 ⋅152809.

It is a cyclic number.

It is not a de Polignac number, because 18165661 - 2¹⁹ = 17641373 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (18165601) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 5745 + ... + 8326.

It is an arithmetic number, because the mean of its divisors is an integer number (4545256).

Almost surely, 2^18165661 is an apocalyptic number.

It is an amenable number.

18165661 is a deficient number, since it is larger than the sum of its proper divisors (15363).

18165661 is a wasteful number, since it uses less digits than its factorization.

18165661 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 15362.

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

The square root of 18165661 is about 4262.1193085131. The cubic root of 18165661 is about 262.8756755516.

The spelling of 18165661 in words is "eighteen million, one hundred sixty-five thousand, six hundred sixty-one".