21593521 has 2 divisors, whose sum is σ = 21593522. Its totient is φ = 21593520.

The previous prime is 21593513. The next prime is 21593569. The reversal of 21593521 is 12539512.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 12503296 + 9090225 = 3536^2 + 3015^2 .

It is a cyclic number.

It is not a de Polignac number, because 21593521 - 2³ = 21593513 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21593521.

It is not a weakly prime, because it can be changed into another prime (21593501) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10796760 + 10796761.

It is an arithmetic number, because the mean of its divisors is an integer number (10796761).

Almost surely, 2^21593521 is an apocalyptic number.

It is an amenable number.

21593521 is a deficient number, since it is larger than the sum of its proper divisors (1).

21593521 is an equidigital number, since it uses as much as digits as its factorization.

21593521 is an evil number, because the sum of its binary digits is even.

The product of its digits is 2700, while the sum is 28.

The square root of 21593521 is about 4646.8829337525. The cubic root of 21593521 is about 278.4674819970.

The spelling of 21593521 in words is "twenty-one million, five hundred ninety-three thousand, five hundred twenty-one".