1991822897 has 2 divisors, whose sum is σ = 1991822898. Its totient is φ = 1991822896.

The previous prime is 1991822891. The next prime is 1991822933. The reversal of 1991822897 is 7982281991.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 1571408881 + 420414016 = 39641^2 + 20504^2 .

It is a cyclic number.

It is not a de Polignac number, because 1991822897 - 2²⁸ = 1723387441 is a prime.

It is not a weakly prime, because it can be changed into another prime (1991822891) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 995911448 + 995911449.

It is an arithmetic number, because the mean of its divisors is an integer number (995911449).

Almost surely, 2^1991822897 is an apocalyptic number.

It is an amenable number.

1991822897 is a deficient number, since it is larger than the sum of its proper divisors (1).

1991822897 is an equidigital number, since it uses as much as digits as its factorization.

1991822897 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 1306368, while the sum is 56.

The square root of 1991822897 is about 44629.8431209432. The cubic root of 1991822897 is about 1258.2016204033.

The spelling of 1991822897 in words is "one billion, nine hundred ninety-one million, eight hundred twenty-two thousand, eight hundred ninety-seven".