991215893 has 2 divisors, whose sum is σ = 991215894. Its totient is φ = 991215892.

The previous prime is 991215887. The next prime is 991215899. The reversal of 991215893 is 398512199.

It is a balanced prime because it is at equal distance from previous prime (991215887) and next prime (991215899).

It can be written as a sum of positive squares in only one way, i.e., 950982244 + 40233649 = 30838^2 + 6343^2 .

It is an emirp because it is prime and its reverse (398512199) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 991215893 - 2¹⁴ = 991199509 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (991215899) 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, 495607946 + 495607947.

It is an arithmetic number, because the mean of its divisors is an integer number (495607947).

Almost surely, 2^991215893 is an apocalyptic number.

It is an amenable number.

991215893 is a deficient number, since it is larger than the sum of its proper divisors (1).

991215893 is an equidigital number, since it uses as much as digits as its factorization.

991215893 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 174960, while the sum is 47.

The square root of 991215893 is about 31483.5813242395. The cubic root of 991215893 is about 997.0633488552.

The spelling of 991215893 in words is "nine hundred ninety-one million, two hundred fifteen thousand, eight hundred ninety-three".