99991009 has 2 divisors, whose sum is σ = 99991010. Its totient is φ = 99991008.

The previous prime is 99990973. The next prime is 99991033. The reversal of 99991009 is 90019999.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 96963409 + 3027600 = 9847^2 + 1740^2 .

It is a cyclic number.

It is not a de Polignac number, because 99991009 - 2¹¹ = 99988961 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 99991009.

It is not a weakly prime, because it can be changed into another prime (99991049) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 49995504 + 49995505.

It is an arithmetic number, because the mean of its divisors is an integer number (49995505).

Almost surely, 2^99991009 is an apocalyptic number.

It is an amenable number.

99991009 is a deficient number, since it is larger than the sum of its proper divisors (1).

99991009 is an equidigital number, since it uses as much as digits as its factorization.

99991009 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 59049, while the sum is 46.

The square root of 99991009 is about 9999.5504398948. The cubic root of 99991009 is about 464.1449721026.

The spelling of 99991009 in words is "ninety-nine million, nine hundred ninety-one thousand, nine".