6681991 has 4 divisors (see below), whose sum is σ = 6711400. Its totient is φ = 6652584.

The previous prime is 6681989. The next prime is 6682007. The reversal of 6681991 is 1991866.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 6681991 - 2¹ = 6681989 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 (6681931) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 14361 + ... + 14818.

It is an arithmetic number, because the mean of its divisors is an integer number (1677850).

Almost surely, 2^6681991 is an apocalyptic number.

6681991 is a deficient number, since it is larger than the sum of its proper divisors (29409).

6681991 is a wasteful number, since it uses less digits than its factorization.

6681991 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 29408.

The product of its digits is 23328, while the sum is 40.

The square root of 6681991 is about 2584.9547384819. The cubic root of 6681991 is about 188.3513029208.

The spelling of 6681991 in words is "six million, six hundred eighty-one thousand, nine hundred ninety-one".