21244915 has 4 divisors (see below), whose sum is σ = 25493904. Its totient is φ = 16995928.

The previous prime is 21244913. The next prime is 21244921. The reversal of 21244915 is 51944212.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21244915 - 2¹ = 21244913 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21244913) 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, 2124487 + ... + 2124496.

It is an arithmetic number, because the mean of its divisors is an integer number (6373476).

Almost surely, 2^21244915 is an apocalyptic number.

21244915 is a deficient number, since it is larger than the sum of its proper divisors (4248989).

21244915 is an equidigital number, since it uses as much as digits as its factorization.

21244915 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4248988.

The product of its digits is 2880, while the sum is 28.

The square root of 21244915 is about 4609.2206499581. The cubic root of 21244915 is about 276.9608176146.

The spelling of 21244915 in words is "twenty-one million, two hundred forty-four thousand, nine hundred fifteen".