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6661 is a prime number

6661 has 2 divisors, whose sum is σ = 6662. Its totient is φ = 6660.

The previous prime is 6659. The next prime is 6673. The reversal of 6661 is 1666.

It is a happy number.

6661 is an esthetic number in base 9, because in such base its adjacent digits differ by 1.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 6561 + 100 = 81^2 + 10^2 .

It is a cyclic number.

It is not a de Polignac number, because 6661 - 21 = 6659 is a prime.

Together with 6659, it forms a pair of twin primes.

It is a Chen prime.

6661 is a lucky number.

It is a nialpdrome in base 10.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (6691) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (5) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 3330 + 3331.

It is an arithmetic number, because the mean of its divisors is an integer number (3331).

26661 is an apocalyptic number.

6661 is the 37-th centered decagonal number.

It is an amenable number.

6661 is a deficient number, since it is larger than the sum of its proper divisors (1).

6661 is an equidigital number, since it uses as much as digits as its factorization.

6661 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 216, while the sum is 19.

The square root of 6661 is about 81.6149496110. The cubic root of 6661 is about 18.8153865285.

The spelling of 6661 in words is "six thousand, six hundred sixty-one".