991297920007 has 4 divisors (see below), whose sum is σ = 991504919560. Its totient is φ = 991090920456.

The previous prime is 991297919959. The next prime is 991297920047. The reversal of 991297920007 is 700029792199.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 991297920007 - 2²⁷ = 991163702279 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 991297920007.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (991297920047) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 103492593 + ... + 103502170.

It is an arithmetic number, because the mean of its divisors is an integer number (247876229890).

Almost surely, 2^991297920007 is an apocalyptic number.

991297920007 is a deficient number, since it is larger than the sum of its proper divisors (206999553).

991297920007 is a wasteful number, since it uses less digits than its factorization.

991297920007 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 206999552.

The product of its (nonzero) digits is 1285956, while the sum is 55.

The spelling of 991297920007 in words is "nine hundred ninety-one billion, two hundred ninety-seven million, nine hundred twenty thousand, seven".