21597253 has 4 divisors (see below), whose sum is σ = 22536288. Its totient is φ = 20658220.

The previous prime is 21597241. The next prime is 21597263. The reversal of 21597253 is 35279512.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 21597253 - 2⁵ = 21597221 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21597263) 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, 469483 + ... + 469528.

It is an arithmetic number, because the mean of its divisors is an integer number (5634072).

Almost surely, 2^21597253 is an apocalyptic number.

21597253 is a gapful number since it is divisible by the number (23) formed by its first and last digit.

It is an amenable number.

21597253 is a deficient number, since it is larger than the sum of its proper divisors (939035).

21597253 is an equidigital number, since it uses as much as digits as its factorization.

21597253 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 939034.

The product of its digits is 18900, while the sum is 34.

The square root of 21597253 is about 4647.2844759063. The cubic root of 21597253 is about 278.4835235491.

The spelling of 21597253 in words is "twenty-one million, five hundred ninety-seven thousand, two hundred fifty-three".