21308593 has 4 divisors (see below), whose sum is σ = 21328228. Its totient is φ = 21288960.

The previous prime is 21308579. The next prime is 21308611. The reversal of 21308593 is 39580312.

It is a happy number.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 18722929 + 2585664 = 4327^2 + 1608^2 .

It is a cyclic number.

It is not a de Polignac number, because 21308593 - 2⁹ = 21308081 is a prime.

It is a super-2 number, since 2×21308593² = 908112271279298, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21308543) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 8088 + ... + 10393.

It is an arithmetic number, because the mean of its divisors is an integer number (5332057).

Almost surely, 2^21308593 is an apocalyptic number.

It is an amenable number.

21308593 is a deficient number, since it is larger than the sum of its proper divisors (19635).

21308593 is a wasteful number, since it uses less digits than its factorization.

21308593 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 19634.

The product of its (nonzero) digits is 6480, while the sum is 31.

The square root of 21308593 is about 4616.1231569359. The cubic root of 21308593 is about 277.2372558371.

The spelling of 21308593 in words is "twenty-one million, three hundred eight thousand, five hundred ninety-three".