21302681 has 2 divisors, whose sum is σ = 21302682. Its totient is φ = 21302680.

The previous prime is 21302663. The next prime is 21302707. The reversal of 21302681 is 18620312.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 18412681 + 2890000 = 4291^2 + 1700^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21302681 is a prime.

It is a super-2 number, since 2×21302681² = 907608435575522, which contains 22 as substring.

It is a Sophie Germain prime.

It is a Chen prime.

It is a Curzon number.

It is not a weakly prime, because it can be changed into another prime (21302651) 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, 10651340 + 10651341.

It is an arithmetic number, because the mean of its divisors is an integer number (10651341).

Almost surely, 2^21302681 is an apocalyptic number.

It is an amenable number.

21302681 is a deficient number, since it is larger than the sum of its proper divisors (1).

21302681 is an equidigital number, since it uses as much as digits as its factorization.

21302681 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 576, while the sum is 23.

The square root of 21302681 is about 4615.4827483157. The cubic root of 21302681 is about 277.2116139398.

Adding to 21302681 its reverse (18620312), we get a palindrome (39922993).

The spelling of 21302681 in words is "twenty-one million, three hundred two thousand, six hundred eighty-one".