199991899981 has 2 divisors, whose sum is σ = 199991899982. Its totient is φ = 199991899980.

The previous prime is 199991899969. The next prime is 199991900029. The reversal of 199991899981 is 189998199991.

199991899981 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 101213695881 + 98778204100 = 318141^2 + 314290^2 .

It is an emirp because it is prime and its reverse (189998199991) is a distict prime. It is also a bemirp because it and its reverse can be mirrored producing other two distinct primes, 186668166661 and 166661866681.

It is a cyclic number.

It is not a de Polignac number, because 199991899981 - 2¹¹ = 199991897933 is a prime.

It is a super-2 number, since 2×199991899981² (a number of 23 digits) contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 199991899895 and 199991899904.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (199991899901) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 99995949990 + 99995949991.

It is an arithmetic number, because the mean of its divisors is an integer number (99995949991).

Almost surely, 2^199991899981 is an apocalyptic number.

It is an amenable number.

199991899981 is a deficient number, since it is larger than the sum of its proper divisors (1).

199991899981 is an equidigital number, since it uses as much as digits as its factorization.

199991899981 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 306110016, while the sum is 82.

The spelling of 199991899981 in words is "one hundred ninety-nine billion, nine hundred ninety-one million, eight hundred ninety-nine thousand, nine hundred eighty-one".