21728593 has 2 divisors, whose sum is σ = 21728594. Its totient is φ = 21728592.

The previous prime is 21728591. The next prime is 21728621. The reversal of 21728593 is 39582712.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 17918289 + 3810304 = 4233^2 + 1952^2 .

It is a cyclic number.

It is not a de Polignac number, because 21728593 - 2¹ = 21728591 is a prime.

Together with 21728591, it forms a pair of twin primes.

It is not a weakly prime, because it can be changed into another prime (21728591) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10864296 + 10864297.

It is an arithmetic number, because the mean of its divisors is an integer number (10864297).

Almost surely, 2^21728593 is an apocalyptic number.

It is an amenable number.

21728593 is a deficient number, since it is larger than the sum of its proper divisors (1).

21728593 is an equidigital number, since it uses as much as digits as its factorization.

21728593 is an evil number, because the sum of its binary digits is even.

The product of its digits is 30240, while the sum is 37.

The square root of 21728593 is about 4661.3938902436. The cubic root of 21728593 is about 279.0468997009.

The spelling of 21728593 in words is "twenty-one million, seven hundred twenty-eight thousand, five hundred ninety-three".