21666341 has 2 divisors, whose sum is σ = 21666342. Its totient is φ = 21666340.

The previous prime is 21666329. The next prime is 21666343. The reversal of 21666341 is 14366612.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 21436900 + 229441 = 4630^2 + 479^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21666341 is a prime.

It is a Sophie Germain prime.

Together with 21666343, it forms a pair of twin primes.

It is a Chen prime.

It is a Curzon number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21666343) 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, 10833170 + 10833171.

It is an arithmetic number, because the mean of its divisors is an integer number (10833171).

Almost surely, 2^21666341 is an apocalyptic number.

It is an amenable number.

21666341 is a deficient number, since it is larger than the sum of its proper divisors (1).

21666341 is an equidigital number, since it uses as much as digits as its factorization.

21666341 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 5184, while the sum is 29.

The square root of 21666341 is about 4654.7116989133. The cubic root of 21666341 is about 278.7801568049.

The spelling of 21666341 in words is "twenty-one million, six hundred sixty-six thousand, three hundred forty-one".