991596891 has 16 divisors (see below), whose sum is σ = 1339388928. Its totient is φ = 652476000.

The previous prime is 991596889. The next prime is 991596911. The reversal of 991596891 is 198695199.

It is not a de Polignac number, because 991596891 - 2¹ = 991596889 is a prime.

It is not an unprimeable number, because it can be changed into a prime (991596841) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 95350 + ... + 105236.

It is an arithmetic number, because the mean of its divisors is an integer number (83711808).

Almost surely, 2^991596891 is an apocalyptic number.

991596891 is a deficient number, since it is larger than the sum of its proper divisors (347792037).

991596891 is a wasteful number, since it uses less digits than its factorization.

991596891 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10322.

The product of its digits is 1574640, while the sum is 57.

The square root of 991596891 is about 31489.6314840298. The cubic root of 991596891 is about 997.1910810284.

The spelling of 991596891 in words is "nine hundred ninety-one million, five hundred ninety-six thousand, eight hundred ninety-one".