21260021 has 2 divisors, whose sum is σ = 21260022. Its totient is φ = 21260020.

The previous prime is 21260011. The next prime is 21260039. The reversal of 21260021 is 12006212.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 21252100 + 7921 = 4610^2 + 89^2 .

It is a cyclic number.

It is not a de Polignac number, because 21260021 - 2⁶ = 21259957 is a prime.

It is a Chen prime.

It is a junction number, because it is equal to n+sod(n) for n = 21259978 and 21260005.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21260011) 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, 10630010 + 10630011.

It is an arithmetic number, because the mean of its divisors is an integer number (10630011).

Almost surely, 2^21260021 is an apocalyptic number.

It is an amenable number.

21260021 is a deficient number, since it is larger than the sum of its proper divisors (1).

21260021 is an equidigital number, since it uses as much as digits as its factorization.

21260021 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 48, while the sum is 14.

The square root of 21260021 is about 4610.8590305929. The cubic root of 21260021 is about 277.0264455369.

Adding to 21260021 its reverse (12006212), we get a palindrome (33266233).

The spelling of 21260021 in words is "twenty-one million, two hundred sixty thousand, twenty-one".