21666037 has 2 divisors, whose sum is σ = 21666038. Its totient is φ = 21666036.

The previous prime is 21666019. The next prime is 21666049. The reversal of 21666037 is 73066612.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 17230801 + 4435236 = 4151^2 + 2106^2 .

It is a cyclic number.

It is not a de Polignac number, because 21666037 - 2¹¹ = 21663989 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21666077) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a good prime.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10833018 + 10833019.

It is an arithmetic number, because the mean of its divisors is an integer number (10833019).

Almost surely, 2^21666037 is an apocalyptic number.

It is an amenable number.

21666037 is a deficient number, since it is larger than the sum of its proper divisors (1).

21666037 is an equidigital number, since it uses as much as digits as its factorization.

21666037 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 9072, while the sum is 31.

The square root of 21666037 is about 4654.6790437150. The cubic root of 21666037 is about 278.7788529459.

The spelling of 21666037 in words is "twenty-one million, six hundred sixty-six thousand, thirty-seven".