21233521 has 4 divisors (see below), whose sum is σ = 21363952. Its totient is φ = 21103092.

The previous prime is 21233503. The next prime is 21233579. The reversal of 21233521 is 12533212.

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 21233521 - 2¹¹ = 21231473 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21233321) 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, 64971 + ... + 65296.

It is an arithmetic number, because the mean of its divisors is an integer number (5340988).

Almost surely, 2^21233521 is an apocalyptic number.

It is an amenable number.

21233521 is a deficient number, since it is larger than the sum of its proper divisors (130431).

21233521 is a wasteful number, since it uses less digits than its factorization.

21233521 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 130430.

The product of its digits is 360, while the sum is 19.

The square root of 21233521 is about 4607.9844834808. The cubic root of 21233521 is about 276.9112958683.

Adding to 21233521 its reverse (12533212), we get a palindrome (33766733).

It can be divided in two parts, 212 and 33521, that added together give a palindrome (33733).

The spelling of 21233521 in words is "twenty-one million, two hundred thirty-three thousand, five hundred twenty-one".