199996991 has 2 divisors, whose sum is σ = 199996992. Its totient is φ = 199996990.

The previous prime is 199996987. The next prime is 199996997. The reversal of 199996991 is 199699991.

It is a weak prime.

It is an emirp because it is prime and its reverse (199699991) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 199996991 - 2² = 199996987 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (199996997) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 99998495 + 99998496.

It is an arithmetic number, because the mean of its divisors is an integer number (99998496).

Almost surely, 2^199996991 is an apocalyptic number.

199996991 is a deficient number, since it is larger than the sum of its proper divisors (1).

199996991 is an equidigital number, since it uses as much as digits as its factorization.

199996991 is an evil number, because the sum of its binary digits is even.

The product of its digits is 3188646, while the sum is 62.

The square root of 199996991 is about 14142.0292391156. The cubic root of 199996991 is about 584.8006148381.

The spelling of 199996991 in words is "one hundred ninety-nine million, nine hundred ninety-six thousand, nine hundred ninety-one".