199990810891 has 2 divisors, whose sum is σ = 199990810892. Its totient is φ = 199990810890.

The previous prime is 199990810879. The next prime is 199990810909. The reversal of 199990810891 is 198018099991.

It is a happy number.

It is a weak prime.

It is an emirp because it is prime and its reverse (198018099991) is a distict prime. It is also a bemirp because it and its reverse can be mirrored producing other two distinct primes, 168018066661 and 166660810861.

It is a cyclic number.

It is not a de Polignac number, because 199990810891 - 2¹⁹ = 199990286603 is a prime.

It is not a weakly prime, because it can be changed into another prime (199990810861) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 99995405445 + 99995405446.

It is an arithmetic number, because the mean of its divisors is an integer number (99995405446).

Almost surely, 2^199990810891 is an apocalyptic number.

199990810891 is a deficient number, since it is larger than the sum of its proper divisors (1).

199990810891 is an equidigital number, since it uses as much as digits as its factorization.

199990810891 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 3779136, while the sum is 64.

The spelling of 199990810891 in words is "one hundred ninety-nine billion, nine hundred ninety million, eight hundred ten thousand, eight hundred ninety-one".