6991857 has 12 divisors (see below), whose sum is σ = 10204740. Its totient is φ = 4612608.

The previous prime is 6991847. The next prime is 6991877. The reversal of 6991857 is 7581996.

It can be written as a sum of positive squares in 2 ways, for example, as 3837681 + 3154176 = 1959^2 + 1776^2 .

It is not a de Polignac number, because 6991857 - 2⁴ = 6991841 is a prime.

It is not an unprimeable number, because it can be changed into a prime (6991847) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 3132 + ... + 4877.

It is an arithmetic number, because the mean of its divisors is an integer number (850395).

Almost surely, 2^6991857 is an apocalyptic number.

It is an amenable number.

6991857 is a deficient number, since it is larger than the sum of its proper divisors (3212883).

6991857 is a wasteful number, since it uses less digits than its factorization.

6991857 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 8112 (or 8109 counting only the distinct ones).

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

The square root of 6991857 is about 2644.2119809123. The cubic root of 6991857 is about 191.2189133120.

It can be divided in two parts, 699 and 1857, that added together give a triangular number (2556 = T₇₁).

The spelling of 6991857 in words is "six million, nine hundred ninety-one thousand, eight hundred fifty-seven".