991297919978 has 8 divisors (see below), whose sum is σ = 1486994798880. Its totient is φ = 495632987020.

The previous prime is 991297919959. The next prime is 991297920047. The reversal of 991297919978 is 879919792199.

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

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 7908758 + ... + 8033121.

It is an arithmetic number, because the mean of its divisors is an integer number (185874349860).

Almost surely, 2^991297919978 is an apocalyptic number.

991297919978 is a deficient number, since it is larger than the sum of its proper divisors (495696878902).

991297919978 is a wasteful number, since it uses less digits than its factorization.

991297919978 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 15972972.

The product of its digits is 416649744, while the sum is 80.

The spelling of 991297919978 in words is "nine hundred ninety-one billion, two hundred ninety-seven million, nine hundred nineteen thousand, nine hundred seventy-eight".