1991068857 has 32 divisors (see below), whose sum is σ = 2997631360. Its totient is φ = 1322277696.

The previous prime is 1991068847. The next prime is 1991068873. The reversal of 1991068857 is 7588601991.

It is not a de Polignac number, because 1991068857 - 2⁸ = 1991068601 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1991068817) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 617313 + ... + 620529.

It is an arithmetic number, because the mean of its divisors is an integer number (93675980).

Almost surely, 2^1991068857 is an apocalyptic number.

It is an amenable number.

1991068857 is a deficient number, since it is larger than the sum of its proper divisors (1006562503).

1991068857 is an frugal number, since it uses more digits than its factorization.

1991068857 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3521 (or 3503 counting only the distinct ones).

The product of its (nonzero) digits is 1088640, while the sum is 54.

The square root of 1991068857 is about 44621.3946106573. The cubic root of 1991068857 is about 1258.0428288266.

The spelling of 1991068857 in words is "one billion, nine hundred ninety-one million, sixty-eight thousand, eight hundred fifty-seven".