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BaseRepresentation
bin100100011111001
3221121220
410203321
51044211
6222253
7105315
oct44371
927556
1018681
1113043
12a989
138670
146b45
155806
hex48f9

18681 has 8 divisors (see below), whose sum is σ = 26880. Its totient is φ = 11472.

The previous prime is 18679. The next prime is 18691.

18681 is nontrivially palindromic in base 10.

18681 is digitally balanced in base 4, because in such base it contains all the possibile digits an equal number of times.

18681 is an esthetic number in base 12, because in such base its adjacent digits differ by 1.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 18681 - 21 = 18679 is a prime.

It is a super-2 number, since 2×186812 = 697959522, which contains 22 as substring.

It is an Ulam number.

It is a Curzon number.

18681 is a lucky number.

It is not an unprimeable number, because it can be changed into a prime (18661) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 201 + ... + 278.

It is an arithmetic number, because the mean of its divisors is an integer number (3360).

218681 is an apocalyptic number.

It is an amenable number.

18681 is a deficient number, since it is larger than the sum of its proper divisors (8199).

18681 is a wasteful number, since it uses less digits than its factorization.

18681 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 495.

The product of its digits is 384, while the sum is 24.

The square root of 18681 is about 136.6784547762. The cubic root of 18681 is about 26.5338359767.

The spelling of 18681 in words is "eighteen thousand, six hundred eighty-one".

Divisors: 1 3 13 39 479 1437 6227 18681