199999309 has 2 divisors, whose sum is σ = 199999310.
Its totient is φ = 199999308.
The previous prime is 199999307. The next prime is 199999333. The reversal of 199999309 is 903999991.
It is a happy number.
It is a weak prime.
It can be written as a sum of positive squares in only one way, i.e., 137241225 + 62758084 = 11715^2 + 7922^2
It is an emirp because it is prime and its reverse (903999991) is a distict prime.
It is a cyclic number.
It is not a de Polignac number, because 199999309 - 21 = 199999307 is a prime.
Together with 199999307, it forms a pair of twin primes.
It is a Chen prime.
It is a congruent number.
It is not a weakly prime, because it can be changed into another prime (199999307) by changing a digit.
It is a polite number, since it can be written as a sum of consecutive naturals, namely, 99999654 + 99999655.
It is an arithmetic number, because the mean of its divisors is an integer number (99999655).
Almost surely, 2199999309 is an apocalyptic number.
It is an amenable number.
199999309 is a deficient number, since it is larger than the sum of its proper divisors (1).
199999309 is an equidigital number, since it uses as much as digits as its factorization.
199999309 is an evil number, because the sum of its binary digits is even.
The product of its (nonzero) digits is 1594323, while the sum is 58.
The square root of 199999309 is about 14142.1111931706.
Note that the first 4 decimals coincide.
The cubic root of 199999309 is about 584.8028741430.
The spelling of 199999309 in words is "one hundred ninety-nine million, nine hundred ninety-nine thousand, three hundred nine".