991564709 has 2 divisors, whose sum is σ = 991564710. Its totient is φ = 991564708.

The previous prime is 991564681. The next prime is 991564727. The reversal of 991564709 is 907465199.

991564709 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 823862209 + 167702500 = 28703^2 + 12950^2 .

It is a cyclic number.

It is not a de Polignac number, because 991564709 - 2²⁰ = 990516133 is a prime.

It is a Sophie Germain prime.

It is a Chen prime.

It is a Curzon number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (991564759) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 495782354 + 495782355.

It is an arithmetic number, because the mean of its divisors is an integer number (495782355).

Almost surely, 2^991564709 is an apocalyptic number.

It is an amenable number.

991564709 is a deficient number, since it is larger than the sum of its proper divisors (1).

991564709 is an equidigital number, since it uses as much as digits as its factorization.

991564709 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 612360, while the sum is 50.

The square root of 991564709 is about 31489.1204862886. The cubic root of 991564709 is about 997.1802930590.

The spelling of 991564709 in words is "nine hundred ninety-one million, five hundred sixty-four thousand, seven hundred nine".