21605593 has 2 divisors, whose sum is σ = 21605594. Its totient is φ = 21605592.

The previous prime is 21605587. The next prime is 21605611. The reversal of 21605593 is 39550612.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 18688329 + 2917264 = 4323^2 + 1708^2 .

It is a cyclic number.

It is not a de Polignac number, because 21605593 - 2⁵ = 21605561 is a prime.

It is not a weakly prime, because it can be changed into another prime (21605093) 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, 10802796 + 10802797.

It is an arithmetic number, because the mean of its divisors is an integer number (10802797).

Almost surely, 2^21605593 is an apocalyptic number.

It is an amenable number.

21605593 is a deficient number, since it is larger than the sum of its proper divisors (1).

21605593 is an equidigital number, since it uses as much as digits as its factorization.

21605593 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 8100, while the sum is 31.

The square root of 21605593 is about 4648.1816874989. The cubic root of 21605593 is about 278.5193653556.

The spelling of 21605593 in words is "twenty-one million, six hundred five thousand, five hundred ninety-three".