999000991 has 2 divisors, whose sum is σ = 999000992.
Its totient is φ = 999000990.
The previous prime is 999000967. The next prime is 999001007. The reversal of 999000991 is 199000999.
It is a strong prime.
It is a cyclic number.
It is not a de Polignac number, because 999000991 - 211 = 998998943 is a prime.
It is equal to p50799619 and since 999000991 and 50799619 have the same sum of digits, it is a Honaker prime.
It is a congruent number.
It is not a weakly prime, because it can be changed into another prime (999000901) 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, 499500495 + 499500496.
It is an arithmetic number, because the mean of its divisors is an integer number (499500496).
Almost surely, 2999000991 is an apocalyptic number.
999000991 is a deficient number, since it is larger than the sum of its proper divisors (1).
999000991 is an equidigital number, since it uses as much as digits as its factorization.
999000991 is an odious number, because the sum of its binary digits is odd.
The product of its (nonzero) digits is 59049, while the sum is 46.
The square root of 999000991 is about 31606.9769354806.
The cubic root of 999000991 is about 999.6668860474.
Note that the first 3 decimals are identical.
The spelling of 999000991 in words is "nine hundred ninety-nine million, nine hundred ninety-one", and thus it is an aban number.