21224513 has 4 divisors (see below), whose sum is σ = 21238980. Its totient is φ = 21210048.

The previous prime is 21224509. The next prime is 21224521. The reversal of 21224513 is 31542212.

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 6723649 + 14500864 = 2593^2 + 3808^2 .

It is a cyclic number.

It is not a de Polignac number, because 21224513 - 2² = 21224509 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21224503) 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, 4748 + ... + 8061.

It is an arithmetic number, because the mean of its divisors is an integer number (5309745).

Almost surely, 2^21224513 is an apocalyptic number.

It is an amenable number.

21224513 is a deficient number, since it is larger than the sum of its proper divisors (14467).

21224513 is a wasteful number, since it uses less digits than its factorization.

21224513 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 14466.

The product of its digits is 480, while the sum is 20.

The square root of 21224513 is about 4607.0069459466. The cubic root of 21224513 is about 276.8721318538.

Adding to 21224513 its reverse (31542212), we get a palindrome (52766725).

The spelling of 21224513 in words is "twenty-one million, two hundred twenty-four thousand, five hundred thirteen".