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18191 is a prime number
BaseRepresentation
bin100011100001111
3220221202
410130033
51040231
6220115
7104015
oct43417
926852
1018191
1112738
12a63b
138384
1468b5
1555cb
hex470f

18191 has 2 divisors, whose sum is σ = 18192. Its totient is φ = 18190.

The previous prime is 18181. The next prime is 18199. The reversal of 18191 is 19181.

It is a strong prime.

It is an emirp because it is prime and its reverse (19181) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 18191 - 26 = 18127 is a prime.

It is a Sophie Germain prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (18199) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9095 + 9096.

It is an arithmetic number, because the mean of its divisors is an integer number (9096).

218191 is an apocalyptic number.

18191 is a deficient number, since it is larger than the sum of its proper divisors (1).

18191 is an equidigital number, since it uses as much as digits as its factorization.

18191 is an evil number, because the sum of its binary digits is even.

The product of its digits is 72, while the sum is 20.

The square root of 18191 is about 134.8740152883. The cubic root of 18191 is about 26.2997845838.

Subtracting 18191 from its reverse (19181), we obtain a triangular number (990 = T44).

It can be divided in two parts, 181 and 91, that multiplied together give a triangular number (16471 = T181).

The spelling of 18191 in words is "eighteen thousand, one hundred ninety-one".