21413521 has 4 divisors (see below), whose sum is σ = 21935844. Its totient is φ = 20891200.

The previous prime is 21413479. The next prime is 21413531. The reversal of 21413521 is 12531412.

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 8910225 + 12503296 = 2985^2 + 3536^2 .

It is a cyclic number.

It is not a de Polignac number, because 21413521 - 2⁷ = 21413393 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21413531) 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, 261100 + ... + 261181.

It is an arithmetic number, because the mean of its divisors is an integer number (5483961).

Almost surely, 2^21413521 is an apocalyptic number.

It is an amenable number.

21413521 is a deficient number, since it is larger than the sum of its proper divisors (522323).

21413521 is an equidigital number, since it uses as much as digits as its factorization.

21413521 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 522322.

The product of its digits is 240, while the sum is 19.

The square root of 21413521 is about 4627.4745812376. The cubic root of 21413521 is about 277.6915691530.

Adding to 21413521 its reverse (12531412), we get a palindrome (33944933).

The spelling of 21413521 in words is "twenty-one million, four hundred thirteen thousand, five hundred twenty-one".