9991691 has 2 divisors, whose sum is σ = 9991692.
Its totient is φ = 9991690.
The previous prime is 9991673. The next prime is 9991693. The reversal of 9991691 is 1961999.
It is a happy number.
It is a strong prime.
It is a cyclic number.
It is not a de Polignac number, because 9991691 - 210 = 9990667 is a prime.
Together with 9991693, it forms a pair of twin primes.
It is a Chen prime.
It is not a weakly prime, because it can be changed into another prime (9991693) by changing a digit.
It is a pernicious number, because its binary representation contains a prime number (11) of ones.
It is a polite number, since it can be written as a sum of consecutive naturals, namely, 4995845 + 4995846.
It is an arithmetic number, because the mean of its divisors is an integer number (4995846).
Almost surely, 29991691 is an apocalyptic number.
9991691 is a deficient number, since it is larger than the sum of its proper divisors (1).
9991691 is an equidigital number, since it uses as much as digits as its factorization.
9991691 is an odious number, because the sum of its binary digits is odd.
The product of its digits is 39366, while the sum is 44.
The square root of 9991691 is about 3160.9636188985.
The cubic root of 9991691 is about 215.3837818093.
The spelling of 9991691 in words is "nine million, nine hundred ninety-one thousand, six hundred ninety-one".