991798889 has 4 divisors (see below), whose sum is σ = 994561920. Its totient is φ = 989035860.

The previous prime is 991798883. The next prime is 991798901. The reversal of 991798889 is 988897199.

It is a happy number.

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.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-991798889 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (991798883) 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, 1380977 + ... + 1381694.

It is an arithmetic number, because the mean of its divisors is an integer number (248640480).

Almost surely, 2^991798889 is an apocalyptic number.

It is an amenable number.

991798889 is a deficient number, since it is larger than the sum of its proper divisors (2763031).

991798889 is a wasteful number, since it uses less digits than its factorization.

991798889 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2763030.

The product of its digits is 23514624, while the sum is 68.

The square root of 991798889 is about 31492.8386938999. The cubic root of 991798889 is about 997.2587889614.

The spelling of 991798889 in words is "nine hundred ninety-one million, seven hundred ninety-eight thousand, eight hundred eighty-nine".