199991087 has 2 divisors, whose sum is σ = 199991088. Its totient is φ = 199991086.

The previous prime is 199991069. The next prime is 199991117. The reversal of 199991087 is 780199991.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 199991087 - 2¹² = 199986991 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (199991387) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 99995543 + 99995544.

It is an arithmetic number, because the mean of its divisors is an integer number (99995544).

Almost surely, 2^199991087 is an apocalyptic number.

199991087 is a deficient number, since it is larger than the sum of its proper divisors (1).

199991087 is an equidigital number, since it uses as much as digits as its factorization.

199991087 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 367416, while the sum is 53.

The square root of 199991087 is about 14141.8204980830. The cubic root of 199991087 is about 584.7948602568.

The spelling of 199991087 in words is "one hundred ninety-nine million, nine hundred ninety-one thousand, eighty-seven".