21441521 has 4 divisors (see below), whose sum is σ = 21846132. Its totient is φ = 21036912.

The previous prime is 21441493. The next prime is 21441523. The reversal of 21441521 is 12514412.

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 18800896 + 2640625 = 4336^2 + 1625^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21441521 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21441493 and 21441502.

It is not an unprimeable number, because it can be changed into a prime (21441523) 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, 202226 + ... + 202331.

It is an arithmetic number, because the mean of its divisors is an integer number (5461533).

Almost surely, 2^21441521 is an apocalyptic number.

It is an amenable number.

21441521 is a deficient number, since it is larger than the sum of its proper divisors (404611).

21441521 is an equidigital number, since it uses as much as digits as its factorization.

21441521 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 404610.

The product of its digits is 320, while the sum is 20.

The square root of 21441521 is about 4630.4990011877. The cubic root of 21441521 is about 277.8125515518.

Adding to 21441521 its reverse (12514412), we get a palindrome (33955933).

The spelling of 21441521 in words is "twenty-one million, four hundred forty-one thousand, five hundred twenty-one".