21395021 has 2 divisors, whose sum is σ = 21395022. Its totient is φ = 21395020.

The previous prime is 21394949. The next prime is 21395047. The reversal of 21395021 is 12059312.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 12460900 + 8934121 = 3530^2 + 2989^2 .

It is a cyclic number.

It is not a de Polignac number, because 21395021 - 2¹⁸ = 21132877 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21395321) 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, 10697510 + 10697511.

It is an arithmetic number, because the mean of its divisors is an integer number (10697511).

Almost surely, 2^21395021 is an apocalyptic number.

It is an amenable number.

21395021 is a deficient number, since it is larger than the sum of its proper divisors (1).

21395021 is an equidigital number, since it uses as much as digits as its factorization.

21395021 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 540, while the sum is 23.

The square root of 21395021 is about 4625.4752188289. The cubic root of 21395021 is about 277.6115764827.

The spelling of 21395021 in words is "twenty-one million, three hundred ninety-five thousand, twenty-one".