6691 has 2 divisors, whose sum is σ = 6692.
Its totient is φ = 6690.
The previous prime is 6689. The next prime is 6701. The reversal of 6691 is 1966.
It can be divided in two parts, 66 and 91, that multiplied together give a palindrome (6006).
It is a weak prime.
It is a cyclic number.
It is not a de Polignac number, because 6691 - 21 = 6689 is a prime.
Together with 6689, it forms a pair of twin primes.
It is not a weakly prime, because it can be changed into another prime (6661) by changing a digit.
It is a polite number, since it can be written as a sum of consecutive naturals, namely, 3345 + 3346.
It is an arithmetic number, because the mean of its divisors is an integer number (3346).
26691 is an apocalyptic number.
6691 is a deficient number, since it is larger than the sum of its proper divisors (1).
6691 is an equidigital number, since it uses as much as digits as its factorization.
6691 is an evil number, because the sum of its binary digits is even.
The product of its digits is 324, while the sum is 22.
The square root of 6691 is about 81.7985329942.
The cubic root of 6691 is about 18.8435913175.
The spelling of 6691 in words is "six thousand, six hundred ninety-one".