856999991 has 8 divisors (see below), whose sum is σ = 884986368. Its totient is φ = 829035000.

The previous prime is 856999973. The next prime is 857000057. The reversal of 856999991 is 199999658.

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-856999991 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (856999931) 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, 134876 + ... + 141086.

It is an arithmetic number, because the mean of its divisors is an integer number (110623296).

Almost surely, 2^856999991 is an apocalyptic number.

856999991 is a deficient number, since it is larger than the sum of its proper divisors (27986377).

856999991 is a wasteful number, since it uses less digits than its factorization.

856999991 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10693.

The product of its digits is 14171760, while the sum is 65.

The square root of 856999991 is about 29274.5621828918. The cubic root of 856999991 is about 949.8614723218.

The spelling of 856999991 in words is "eight hundred fifty-six million, nine hundred ninety-nine thousand, nine hundred ninety-one".