18163681 has 4 divisors (see below), whose sum is σ = 18471600. Its totient is φ = 17855764.

The previous prime is 18163679. The next prime is 18163693. The reversal of 18163681 is 18636181.

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: 18636181 = 41 ⋅454541.

It is a cyclic number.

It is not a de Polignac number, because 18163681 - 2¹ = 18163679 is a prime.

It is a super-2 number, since 2×18163681² = 659838614939522, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (18163631) 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, 153871 + ... + 153988.

It is an arithmetic number, because the mean of its divisors is an integer number (4617900).

Almost surely, 2^18163681 is an apocalyptic number.

It is an amenable number.

18163681 is a deficient number, since it is larger than the sum of its proper divisors (307919).

18163681 is an equidigital number, since it uses as much as digits as its factorization.

18163681 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 307918.

The product of its digits is 6912, while the sum is 34.

The square root of 18163681 is about 4261.8870233736. The cubic root of 18163681 is about 262.8661243302.

The spelling of 18163681 in words is "eighteen million, one hundred sixty-three thousand, six hundred eighty-one".