991087065 has 12 divisors (see below), whose sum is σ = 1717884324. Its totient is φ = 528579744.

The previous prime is 991087061. The next prime is 991087067. The reversal of 991087065 is 560780199.

It can be written as a sum of positive squares in 2 ways, for example, as 431102169 + 559984896 = 20763^2 + 23664^2 .

It is not a de Polignac number, because 991087065 - 2² = 991087061 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (45), and also a Moran number because the ratio is a prime number: 22024157 = 991087065 / (9 + 9 + 1 + 0 + 8 + 7 + 0 + 6 + 5).

It is a self number, because there is not a number n which added to its sum of digits gives 991087065.

It is not an unprimeable number, because it can be changed into a prime (991087061) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 11012034 + ... + 11012123.

It is an arithmetic number, because the mean of its divisors is an integer number (143157027).

Almost surely, 2^991087065 is an apocalyptic number.

It is an amenable number.

991087065 is a deficient number, since it is larger than the sum of its proper divisors (726797259).

991087065 is a wasteful number, since it uses less digits than its factorization.

991087065 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 22024168 (or 22024165 counting only the distinct ones).

The product of its (nonzero) digits is 136080, while the sum is 45.

The square root of 991087065 is about 31481.5353024594. The cubic root of 991087065 is about 997.0201509864.

The spelling of 991087065 in words is "nine hundred ninety-one million, eighty-seven thousand, sixty-five".