991161212789 has 8 divisors (see below), whose sum is σ = 1081281200160. Its totient is φ = 901043629200.

The previous prime is 991161212777. The next prime is 991161212843. The reversal of 991161212789 is 987212161199.

It is a happy number.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 991161212789 - 2²⁴ = 991144435573 is a prime.

It is a super-2 number, since 2×991161212789² (a number of 25 digits) contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (991161212729) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 322982 + ... + 1444520.

It is an arithmetic number, because the mean of its divisors is an integer number (135160150020).

Almost surely, 2^991161212789 is an apocalyptic number.

It is an amenable number.

991161212789 is a deficient number, since it is larger than the sum of its proper divisors (90119987371).

991161212789 is a wasteful number, since it uses less digits than its factorization.

991161212789 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1201891.

The product of its digits is 979776, while the sum is 56.

The spelling of 991161212789 in words is "nine hundred ninety-one billion, one hundred sixty-one million, two hundred twelve thousand, seven hundred eighty-nine".