18384221 has 2 divisors, whose sum is σ = 18384222. Its totient is φ = 18384220.
The previous prime is 18384211. The next prime is 18384239. The reversal of 18384221 is 12248381.
It is a weak prime.
It can be written as a sum of positive squares in only one way, i.e., 18232900 + 151321 = 4270^2 + 389^2 .
It is a cyclic number.
It is not a de Polignac number, because 18384221 - 218 = 18122077 is a prime.
It is a Sophie Germain prime.
It is a Curzon number.
It is a congruent number.
It is not a weakly prime, because it can be changed into another prime (18384211) by changing a digit.
It is a pernicious number, because its binary representation contains a prime number (11) of ones.
It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9192110 + 9192111.
It is an arithmetic number, because the mean of its divisors is an integer number (9192111).
Almost surely, 218384221 is an apocalyptic number.
It is an amenable number.
18384221 is a deficient number, since it is larger than the sum of its proper divisors (1).
18384221 is an equidigital number, since it uses as much as digits as its factorization.
18384221 is an odious number, because the sum of its binary digits is odd.
The product of its digits is 3072, while the sum is 29.
The square root of 18384221 is about 4287.6824742511. The cubic root of 18384221 is about 263.9257376445.
The spelling of 18384221 in words is "eighteen million, three hundred eighty-four thousand, two hundred twenty-one".
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