21005293 has 2 divisors, whose sum is σ = 21005294. Its totient is φ = 21005292.

The previous prime is 21005291. The next prime is 21005297. The reversal of 21005293 is 39250012.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 10778089 + 10227204 = 3283^2 + 3198^2 .

It is a cyclic number.

It is not a de Polignac number, because 21005293 - 2¹ = 21005291 is a prime.

Together with 21005291, it forms a pair of twin primes.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21005291) 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, 10502646 + 10502647.

It is an arithmetic number, because the mean of its divisors is an integer number (10502647).

Almost surely, 2^21005293 is an apocalyptic number.

It is an amenable number.

21005293 is a deficient number, since it is larger than the sum of its proper divisors (1).

21005293 is an equidigital number, since it uses as much as digits as its factorization.

21005293 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 22.

The square root of 21005293 is about 4583.1531722167. The cubic root of 21005293 is about 275.9155950333.

The spelling of 21005293 in words is "twenty-one million, five thousand, two hundred ninety-three".