21443521 has 16 divisors (see below), whose sum is σ = 24634368. Its totient is φ = 18475600.

The previous prime is 21443519. The next prime is 21443561. The reversal of 21443521 is 12534412.

It is not a de Polignac number, because 21443521 - 2¹ = 21443519 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21443492 and 21443501.

It is not an unprimeable number, because it can be changed into a prime (21443561) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 32820 + ... + 33466.

It is an arithmetic number, because the mean of its divisors is an integer number (1539648).

Almost surely, 2^21443521 is an apocalyptic number.

It is an amenable number.

21443521 is a deficient number, since it is larger than the sum of its proper divisors (3190847).

21443521 is a wasteful number, since it uses less digits than its factorization.

21443521 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 812.

The product of its digits is 960, while the sum is 22.

The square root of 21443521 is about 4630.7149555981. The cubic root of 21443521 is about 277.8211891205.

Adding to 21443521 its reverse (12534412), we get a palindrome (33977933).

It can be divided in two parts, 2144 and 3521, that added together give a palindrome (5665).

The spelling of 21443521 in words is "twenty-one million, four hundred forty-three thousand, five hundred twenty-one".