21202681 has 2 divisors, whose sum is σ = 21202682. Its totient is φ = 21202680.

The previous prime is 21202669. The next prime is 21202717. The reversal of 21202681 is 18620212.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 18020025 + 3182656 = 4245^2 + 1784^2 .

It is a cyclic number.

It is not a de Polignac number, because 21202681 - 2¹¹ = 21200633 is a prime.

It is a super-2 number, since 2×21202681² = 899107363175522, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (21200681) by changing a digit.

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

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10601340 + 10601341.

It is an arithmetic number, because the mean of its divisors is an integer number (10601341).

Almost surely, 2^21202681 is an apocalyptic number.

It is an amenable number.

21202681 is a deficient number, since it is larger than the sum of its proper divisors (1).

21202681 is an equidigital number, since it uses as much as digits as its factorization.

21202681 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 384, while the sum is 22.

The square root of 21202681 is about 4604.6369020803. The cubic root of 21202681 is about 276.7771670344. Note that the first 3 decimals are identical.

Adding to 21202681 its reverse (18620212), we get a palindrome (39822893).

The spelling of 21202681 in words is "twenty-one million, two hundred two thousand, six hundred eighty-one".