6691891 has 2 divisors, whose sum is σ = 6691892. Its totient is φ = 6691890.

The previous prime is 6691859. The next prime is 6691903. The reversal of 6691891 is 1981966.

6691891 is nontrivially palindromic in base 2.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 6691891 - 2⁵ = 6691859 is a prime.

It is a zygodrome in base 2.

It is not a weakly prime, because it can be changed into another prime (6691801) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 3345945 + 3345946.

It is an arithmetic number, because the mean of its divisors is an integer number (3345946).

Almost surely, 2^6691891 is an apocalyptic number.

6691891 is a deficient number, since it is larger than the sum of its proper divisors (1).

6691891 is an equidigital number, since it uses as much as digits as its factorization.

6691891 is an odious number, because the sum of its binary digits is odd.

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

The square root of 6691891 is about 2586.8689568666. The cubic root of 6691891 is about 188.4442770935. Note that the first 3 decimals are identical.

The spelling of 6691891 in words is "six million, six hundred ninety-one thousand, eight hundred ninety-one".