6857991 has 18 divisors (see below), whose sum is σ = 11524032. Its totient is φ = 3918600.

The previous prime is 6857971. The next prime is 6857999. The reversal of 6857991 is 1997586.

It is not a de Polignac number, because 6857991 - 2⁵ = 6857959 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (6857999) by changing a digit.

It is a polite number, since it can be written in 17 ways as a sum of consecutive naturals, for example, 7335 + ... + 8216.

It is an arithmetic number, because the mean of its divisors is an integer number (640224).

Almost surely, 2^6857991 is an apocalyptic number.

6857991 is a deficient number, since it is larger than the sum of its proper divisors (4666041).

6857991 is a wasteful number, since it uses less digits than its factorization.

6857991 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 15571 (or 15561 counting only the distinct ones).

The product of its digits is 136080, while the sum is 45.

The square root of 6857991 is about 2618.7766227764. The cubic root of 6857991 is about 189.9906828303.

The spelling of 6857991 in words is "six million, eight hundred fifty-seven thousand, nine hundred ninety-one".