1811901991001 has 2 divisors, whose sum is σ = 1811901991002. Its totient is φ = 1811901991000.

The previous prime is 1811901990979. The next prime is 1811901991057. The reversal of 1811901991001 is 1001991091181.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 1811578710601 + 323280400 = 1345949^2 + 17980^2 .

It is an emirp because it is prime and its reverse (1001991091181) is a distict prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-1811901991001 is a prime.

It is a Sophie Germain prime.

It is a Curzon number.

It is a self number, because there is not a number n which added to its sum of digits gives 1811901991001.

It is not a weakly prime, because it can be changed into another prime (1811901991061) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 905950995500 + 905950995501.

It is an arithmetic number, because the mean of its divisors is an integer number (905950995501).

Almost surely, 2^{1811901991001} is an apocalyptic number.

It is an amenable number.

1811901991001 is a deficient number, since it is larger than the sum of its proper divisors (1).

1811901991001 is an equidigital number, since it uses as much as digits as its factorization.

1811901991001 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 5832, while the sum is 41.

The spelling of 1811901991001 in words is "one trillion, eight hundred eleven billion, nine hundred one million, nine hundred ninety-one thousand, one".