21597313 has 4 divisors (see below), whose sum is σ = 21666628. Its totient is φ = 21528000.

The previous prime is 21597287. The next prime is 21597353. The reversal of 21597313 is 31379512.

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 178929 + 21418384 = 423^2 + 4628^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21597313 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21597353) 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, 34188 + ... + 34813.

It is an arithmetic number, because the mean of its divisors is an integer number (5416657).

Almost surely, 2^21597313 is an apocalyptic number.

It is an amenable number.

21597313 is a deficient number, since it is larger than the sum of its proper divisors (69315).

21597313 is an equidigital number, since it uses as much as digits as its factorization.

21597313 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 69314.

The product of its digits is 5670, while the sum is 31.

The square root of 21597313 is about 4647.2909312846. The cubic root of 21597313 is about 278.4837814368.

The spelling of 21597313 in words is "twenty-one million, five hundred ninety-seven thousand, three hundred thirteen".