991645522591 has 2 divisors, whose sum is σ = 991645522592. Its totient is φ = 991645522590.

The previous prime is 991645522559. The next prime is 991645522603. The reversal of 991645522591 is 195225546199.

It is a strong prime.

It is an emirp because it is prime and its reverse (195225546199) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 991645522591 - 2⁵ = 991645522559 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (991645522501) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 495822761295 + 495822761296.

It is an arithmetic number, because the mean of its divisors is an integer number (495822761296).

Almost surely, 2^991645522591 is an apocalyptic number.

991645522591 is a deficient number, since it is larger than the sum of its proper divisors (1).

991645522591 is an equidigital number, since it uses as much as digits as its factorization.

991645522591 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 8748000, while the sum is 58.

The spelling of 991645522591 in words is "nine hundred ninety-one billion, six hundred forty-five million, five hundred twenty-two thousand, five hundred ninety-one".