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BaseRepresentation
bin100011010100001
3220210200
410122201
51034311
6215413
7103500
oct43241
926720
1018081
1112648
12a569
1382cb
146837
155556
hex46a1

18081 has 18 divisors (see below), whose sum is σ = 31122. Its totient is φ = 10080.

The previous prime is 18077. The next prime is 18089.

Adding to 18081 its product of nonzero digits (64), we get a triangular number (18145 = T190).

It is a happy number.

18081 is nontrivially palindromic in base 10.

It can be written as a sum of positive squares in only one way, i.e., 11025 + 7056 = 105^2 + 84^2 .

It is not a de Polignac number, because 18081 - 22 = 18077 is a prime.

It is a super-2 number, since 2×180812 = 653845122, which contains 22 as substring.

18081 is a strobogrammatic number because it is the same when read upside-down.

18081 is a modest number, since divided by 81 gives 18 as remainder.

It is a plaindrome in base 15.

It is a congruent number.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 18081.

It is not an unprimeable number, because it can be changed into a prime (18089) by changing a digit.

It is a polite number, since it can be written in 17 ways as a sum of consecutive naturals, for example, 421 + ... + 461.

It is an arithmetic number, because the mean of its divisors is an integer number (1729).

218081 is an apocalyptic number.

It is an amenable number.

18081 is a deficient number, since it is larger than the sum of its proper divisors (13041).

18081 is a wasteful number, since it uses less digits than its factorization.

18081 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 61 (or 51 counting only the distinct ones).

The product of its (nonzero) digits is 64, while the sum is 18.

The square root of 18081 is about 134.4656089861. The cubic root of 18081 is about 26.2466662433.

The spelling of 18081 in words is "eighteen thousand, eighty-one".