991758779 has 4 divisors (see below), whose sum is σ = 1081918680. Its totient is φ = 901598880.

The previous prime is 991758739. The next prime is 991758809. The reversal of 991758779 is 977857199.

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 991758779 - 2¹² = 991754683 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (991758709) 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 3 ways as a sum of consecutive naturals, for example, 45079934 + ... + 45079955.

It is an arithmetic number, because the mean of its divisors is an integer number (270479670).

Almost surely, 2^991758779 is an apocalyptic number.

991758779 is a deficient number, since it is larger than the sum of its proper divisors (90159901).

991758779 is a wasteful number, since it uses less digits than its factorization.

991758779 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 90159900.

The product of its digits is 10001880, while the sum is 62.

The square root of 991758779 is about 31492.2018760200. The cubic root of 991758779 is about 997.2453451777.

The spelling of 991758779 in words is "nine hundred ninety-one million, seven hundred fifty-eight thousand, seven hundred seventy-nine".