21433521 has 4 divisors (see below), whose sum is σ = 28578032. Its totient is φ = 14289012.

The previous prime is 21433519. The next prime is 21433541. The reversal of 21433521 is 12533412.

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 not a de Polignac number, because 21433521 - 2¹ = 21433519 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (21433541) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3572251 + ... + 3572256.

It is an arithmetic number, because the mean of its divisors is an integer number (7144508).

Almost surely, 2^21433521 is an apocalyptic number.

It is an amenable number.

21433521 is a deficient number, since it is larger than the sum of its proper divisors (7144511).

21433521 is an equidigital number, since it uses as much as digits as its factorization.

21433521 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7144510.

The product of its digits is 720, while the sum is 21.

The square root of 21433521 is about 4629.6350828116. The cubic root of 21433521 is about 277.7779959050. Note that the first 3 decimals are identical.

Adding to 21433521 its reverse (12533412), we get a palindrome (33966933).

The spelling of 21433521 in words is "twenty-one million, four hundred thirty-three thousand, five hundred twenty-one".