21424243 has 12 divisors (see below), whose sum is σ = 22674960. Its totient is φ = 20218016.

The previous prime is 21424241. The next prime is 21424253. The reversal of 21424243 is 34242412.

It is a happy number.

It is not a de Polignac number, because 21424243 - 2¹ = 21424241 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21424241) 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 11 ways as a sum of consecutive naturals, for example, 81330 + ... + 81592.

It is an arithmetic number, because the mean of its divisors is an integer number (1889580).

Almost surely, 2^21424243 is an apocalyptic number.

21424243 is a deficient number, since it is larger than the sum of its proper divisors (1250717).

21424243 is an equidigital number, since it uses as much as digits as its factorization.

21424243 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 398 (or 345 counting only the distinct ones).

The product of its digits is 1536, while the sum is 22.

The square root of 21424243 is about 4628.6329515312. The cubic root of 21424243 is about 277.7379092233.

Adding to 21424243 its reverse (34242412), we get a palindrome (55666655).

The spelling of 21424243 in words is "twenty-one million, four hundred twenty-four thousand, two hundred forty-three".