991571287 has 16 divisors (see below), whose sum is σ = 1171353600. Its totient is φ = 821795040.

The previous prime is 991571281. The next prime is 991571327. The reversal of 991571287 is 782175199.

It is a cyclic number.

It is not a de Polignac number, because 991571287 - 2⁷ = 991571159 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 991571287.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (991571281) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 5514 + ... + 44872.

It is an arithmetic number, because the mean of its divisors is an integer number (73209600).

Almost surely, 2^991571287 is an apocalyptic number.

991571287 is a deficient number, since it is larger than the sum of its proper divisors (179782313).

991571287 is a wasteful number, since it uses less digits than its factorization.

991571287 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 39486.

The product of its digits is 317520, while the sum is 49.

The square root of 991571287 is about 31489.2249348884. The cubic root of 991571287 is about 997.1824981387.

The spelling of 991571287 in words is "nine hundred ninety-one million, five hundred seventy-one thousand, two hundred eighty-seven".