13666021 has 2 divisors, whose sum is σ = 13666022. Its totient is φ = 13666020.

The previous prime is 13666019. The next prime is 13666027. The reversal of 13666021 is 12066631.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 13653025 + 12996 = 3695^2 + 114^2 .

It is a cyclic number.

It is not a de Polignac number, because 13666021 - 2¹ = 13666019 is a prime.

Together with 13666019, it forms a pair of twin primes.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (13666027) 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, 6833010 + 6833011.

It is an arithmetic number, because the mean of its divisors is an integer number (6833011).

Almost surely, 2^13666021 is an apocalyptic number.

It is an amenable number.

13666021 is a deficient number, since it is larger than the sum of its proper divisors (1).

13666021 is an equidigital number, since it uses as much as digits as its factorization.

13666021 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 1296, while the sum is 25.

The square root of 13666021 is about 3696.7581744009. The cubic root of 13666021 is about 239.0822648246.

The spelling of 13666021 in words is "thirteen million, six hundred sixty-six thousand, twenty-one".