21214421 has 4 divisors (see below), whose sum is σ = 21266700. Its totient is φ = 21162144.

The previous prime is 21214381. The next prime is 21214429. The reversal of 21214421 is 12441212.

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 11222500 + 9991921 = 3350^2 + 3161^2 .

It is a cyclic number.

It is not a de Polignac number, because 21214421 - 2¹⁸ = 20952277 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21214421.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21214429) 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, 25526 + ... + 26343.

It is an arithmetic number, because the mean of its divisors is an integer number (5316675).

Almost surely, 2^21214421 is an apocalyptic number.

It is an amenable number.

21214421 is a deficient number, since it is larger than the sum of its proper divisors (52279).

21214421 is an equidigital number, since it uses as much as digits as its factorization.

21214421 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 52278.

The product of its digits is 128, while the sum is 17.

The square root of 21214421 is about 4605.9115275915. The cubic root of 21214421 is about 276.8282417766.

Adding to 21214421 its reverse (12441212), we get a palindrome (33655633).

The spelling of 21214421 in words is "twenty-one million, two hundred fourteen thousand, four hundred twenty-one".