1811993 has 2 divisors, whose sum is σ = 1811994. Its totient is φ = 1811992.

The previous prime is 1811987. The next prime is 1812037. The reversal of 1811993 is 3991181.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 1338649 + 473344 = 1157^2 + 688^2 .

It is an emirp because it is prime and its reverse (3991181) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 1811993 - 2⁸ = 1811737 is a prime.

It is a Sophie Germain prime.

It is a Curzon number.

It is not a weakly prime, because it can be changed into another prime (1811903) 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, 905996 + 905997.

It is an arithmetic number, because the mean of its divisors is an integer number (905997).

2^1811993 is an apocalyptic number.

It is an amenable number.

1811993 is a deficient number, since it is larger than the sum of its proper divisors (1).

1811993 is an equidigital number, since it uses as much as digits as its factorization.

1811993 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 1944, while the sum is 32.

The square root of 1811993 is about 1346.1028935412. The cubic root of 1811993 is about 121.9136045139.

The spelling of 1811993 in words is "one million, eight hundred eleven thousand, nine hundred ninety-three".