21453521 has 4 divisors (see below), whose sum is σ = 21817200. Its totient is φ = 21089844.

The previous prime is 21453493. The next prime is 21453529. The reversal of 21453521 is 12535412.

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 21453521 - 2¹⁸ = 21191377 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21453529) 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 in 3 ways as a sum of consecutive naturals, for example, 181751 + ... + 181868.

It is an arithmetic number, because the mean of its divisors is an integer number (5454300).

Almost surely, 2^21453521 is an apocalyptic number.

It is an amenable number.

21453521 is a deficient number, since it is larger than the sum of its proper divisors (363679).

21453521 is an equidigital number, since it uses as much as digits as its factorization.

21453521 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 363678.

The product of its digits is 1200, while the sum is 23.

The square root of 21453521 is about 4631.7945766193. The cubic root of 21453521 is about 277.8643689095.

Adding to 21453521 its reverse (12535412), we get a palindrome (33988933).

It can be divided in two parts, 214 and 53521, that added together give a palindrome (53735).

The spelling of 21453521 in words is "twenty-one million, four hundred fifty-three thousand, five hundred twenty-one".