21728293 has 2 divisors, whose sum is σ = 21728294. Its totient is φ = 21728292.

The previous prime is 21728269. The next prime is 21728297. The reversal of 21728293 is 39282712.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 21696964 + 31329 = 4658^2 + 177^2 .

It is a cyclic number.

It is not a de Polignac number, because 21728293 - 2⁹ = 21727781 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21728297) 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, 10864146 + 10864147.

It is an arithmetic number, because the mean of its divisors is an integer number (10864147).

Almost surely, 2^21728293 is an apocalyptic number.

It is an amenable number.

21728293 is a deficient number, since it is larger than the sum of its proper divisors (1).

21728293 is an equidigital number, since it uses as much as digits as its factorization.

21728293 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 12096, while the sum is 34.

The square root of 21728293 is about 4661.3617109167. The cubic root of 21728293 is about 279.0456154567.

The spelling of 21728293 in words is "twenty-one million, seven hundred twenty-eight thousand, two hundred ninety-three".