21441821 has 4 divisors (see below), whose sum is σ = 21940512. Its totient is φ = 20943132.

The previous prime is 21441769. The next prime is 21441857. The reversal of 21441821 is 12814412.

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 a cyclic number.

It is not a de Polignac number, because 21441821 - 2¹⁸ = 21179677 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21441881) 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, 249281 + ... + 249366.

It is an arithmetic number, because the mean of its divisors is an integer number (5485128).

Almost surely, 2^21441821 is an apocalyptic number.

It is an amenable number.

21441821 is a deficient number, since it is larger than the sum of its proper divisors (498691).

21441821 is an equidigital number, since it uses as much as digits as its factorization.

21441821 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 498690.

The product of its digits is 512, while the sum is 23.

The square root of 21441821 is about 4630.5313949913. The cubic root of 21441821 is about 277.8138472214.

The spelling of 21441821 in words is "twenty-one million, four hundred forty-one thousand, eight hundred twenty-one".