991207665 has 32 divisors (see below), whose sum is σ = 2013884160. Its totient is φ = 453123072.

The previous prime is 991207631. The next prime is 991207669. The reversal of 991207665 is 566702199.

It is a happy number.

It is not a de Polignac number, because 991207665 - 2⁶ = 991207601 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (45).

It is a self number, because there is not a number n which added to its sum of digits gives 991207665.

It is not an unprimeable number, because it can be changed into a prime (991207669) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 523504 + ... + 525393.

It is an arithmetic number, because the mean of its divisors is an integer number (62933880).

Almost surely, 2^991207665 is an apocalyptic number.

It is an amenable number.

991207665 is an abundant number, since it is smaller than the sum of its proper divisors (1022676495).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

991207665 is a wasteful number, since it uses less digits than its factorization.

991207665 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1048918 (or 1048912 counting only the distinct ones).

The product of its (nonzero) digits is 204120, while the sum is 45.

The square root of 991207665 is about 31483.4506526842. The cubic root of 991207665 is about 997.0605900012.

The spelling of 991207665 in words is "nine hundred ninety-one million, two hundred seven thousand, six hundred sixty-five".