991898000209 has 2 divisors, whose sum is σ = 991898000210. Its totient is φ = 991898000208.

The previous prime is 991898000201. The next prime is 991898000321. The reversal of 991898000209 is 902000898199.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 979759469584 + 12138530625 = 989828^2 + 110175^2 .

It is an emirp because it is prime and its reverse (902000898199) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 991898000209 - 2³ = 991898000201 is a prime.

It is a super-2 number, since 2×991898000209² (a number of 25 digits) contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 991898000209.

It is not a weakly prime, because it can be changed into another prime (991898000201) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 495949000104 + 495949000105.

It is an arithmetic number, because the mean of its divisors is an integer number (495949000105).

Almost surely, 2^991898000209 is an apocalyptic number.

It is an amenable number.

991898000209 is a deficient number, since it is larger than the sum of its proper divisors (1).

991898000209 is an equidigital number, since it uses as much as digits as its factorization.

991898000209 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 839808, while the sum is 55.

The spelling of 991898000209 in words is "nine hundred ninety-one billion, eight hundred ninety-eight million, two hundred nine", and thus it is an aban number.