999199991 has 2 divisors, whose sum is σ = 999199992. Its totient is φ = 999199990.

The previous prime is 999199963. The next prime is 999200003. The reversal of 999199991 is 199991999.

It is a strong prime.

It is an emirp because it is prime and its reverse (199991999) is a distict prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-999199991 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 (999199951) 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, 499599995 + 499599996.

It is an arithmetic number, because the mean of its divisors is an integer number (499599996).

Almost surely, 2^999199991 is an apocalyptic number.

999199991 is a deficient number, since it is larger than the sum of its proper divisors (1).

999199991 is an equidigital number, since it uses as much as digits as its factorization.

999199991 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 4782969, while the sum is 65.

The square root of 999199991 is about 31610.1248178491. The cubic root of 999199991 is about 999.7332591890.

The spelling of 999199991 in words is "nine hundred ninety-nine million, one hundred ninety-nine thousand, nine hundred ninety-one".