1811 has 2 divisors, whose sum is σ = 1812. Its totient is φ = 1810.
The previous prime is 1801. The next prime is 1823. The reversal of 1811 is 1181.
It is a weak prime.
It is an emirp because it is prime and its reverse (1181) is a distict prime.
It is a cyclic number.
It is not a de Polignac number, because 1811 - 26 = 1747 is a prime.
It is a Sophie Germain prime.
It is a nialpdrome in base 13.
It is a junction number, because it is equal to n+sod(n) for n = 1792 and 1801.
It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 1811.
It is not a weakly prime, because it can be changed into another prime (1801) by changing a digit.
It is a polite number, since it can be written as a sum of consecutive naturals, namely, 905 + 906.
It is an arithmetic number, because the mean of its divisors is an integer number (906).
21811 is an apocalyptic number.
1811 is a deficient number, since it is larger than the sum of its proper divisors (1).
1811 is an equidigital number, since it uses as much as digits as its factorization.
1811 is an evil number, because the sum of its binary digits is even.
The product of its digits is 8, while the sum is 11.
The square root of 1811 is about 42.5558456619. Note that the first 3 decimals coincide. The cubic root of 1811 is about 12.1891330268.
Adding to 1811 its reverse (1181), we get a palindrome (2992).
Subtracting from 1811 its reverse (1181), we obtain a triangular number (630 = T35).
The spelling of 1811 in words is "one thousand, eight hundred eleven".
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