91000009 has 2 divisors, whose sum is σ = 91000010. Its totient is φ = 91000008.

The previous prime is 90999989. The next prime is 91000027. The reversal of 91000009 is 90000019.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 57684025 + 33315984 = 7595^2 + 5772^2 .

It is a cyclic number.

It is not a de Polignac number, because 91000009 - 2⁵ = 90999977 is a prime.

It is a Chen prime.

It is a self number, because there is not a number n which added to its sum of digits gives 91000009.

It is not a weakly prime, because it can be changed into another prime (91010009) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 45500004 + 45500005.

It is an arithmetic number, because the mean of its divisors is an integer number (45500005).

Almost surely, 2^91000009 is an apocalyptic number.

It is an amenable number.

91000009 is a deficient number, since it is larger than the sum of its proper divisors (1).

91000009 is an equidigital number, since it uses as much as digits as its factorization.

91000009 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 81, while the sum is 19.

The square root of 91000009 is about 9539.3924858976. The cubic root of 91000009 is about 449.7941593559.

The spelling of 91000009 in words is "ninety-one million, nine", and thus it is an aban number and an uban number.