18121 has 2 divisors, whose sum is σ = 18122. Its totient is φ = 18120.
The previous prime is 18119. The next prime is 18127. The reversal of 18121 is 12181.
It is a weak prime.
It can be written as a sum of positive squares in only one way, i.e., 14400 + 3721 = 120^2 + 61^2 .
It is a cyclic number.
It is not a de Polignac number, because 18121 - 21 = 18119 is a prime.
Together with 18119, it forms a pair of twin primes.
It is an alternating number because its digits alternate between odd and even.
It is a nialpdrome in base 8.
It is not a weakly prime, because it can be changed into another prime (18127) by changing a digit.
It is a pernicious number, because its binary representation contains a prime number (7) of ones.
It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9060 + 9061.
It is an arithmetic number, because the mean of its divisors is an integer number (9061).
218121 is an apocalyptic number.
It is an amenable number.
18121 is a deficient number, since it is larger than the sum of its proper divisors (1).
18121 is an equidigital number, since it uses as much as digits as its factorization.
18121 is an odious number, because the sum of its binary digits is odd.
The product of its digits is 16, while the sum is 13.
The square root of 18121 is about 134.6142637316. The cubic root of 18121 is about 26.2660068661.
It can be divided in two parts, 181 and 21, that added together give a palindrome (202).
The spelling of 18121 in words is "eighteen thousand, one hundred twenty-one".
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