991876789 has 4 divisors (see below), whose sum is σ = 1008688320. Its totient is φ = 975065260.

The previous prime is 991876757. The next prime is 991876799. The reversal of 991876789 is 987678199.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also an emirpimes, since its reverse is a distinct semiprime: 987678199 = 271 ⋅3644569.

It is a cyclic number.

It is not a de Polignac number, because 991876789 - 2⁵ = 991876757 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 991876789.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (991876709) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 8405677 + ... + 8405794.

It is an arithmetic number, because the mean of its divisors is an integer number (252172080).

Almost surely, 2^991876789 is an apocalyptic number.

It is an amenable number.

991876789 is a deficient number, since it is larger than the sum of its proper divisors (16811531).

991876789 is a wasteful number, since it uses less digits than its factorization.

991876789 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 16811530.

The product of its digits is 13716864, while the sum is 64.

The square root of 991876789 is about 31494.0754587272. The cubic root of 991876789 is about 997.2848978923.

The spelling of 991876789 in words is "nine hundred ninety-one million, eight hundred seventy-six thousand, seven hundred eighty-nine".