21424237 has 4 divisors (see below), whose sum is σ = 21775516. Its totient is φ = 21072960.

The previous prime is 21424223. The next prime is 21424241. The reversal of 21424237 is 73242412.

It is a happy number.

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 11062276 + 10361961 = 3326^2 + 3219^2 .

It is a cyclic number.

It is not a de Polignac number, because 21424237 - 2²³ = 13035629 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 (21424217) 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, 175548 + ... + 175669.

It is an arithmetic number, because the mean of its divisors is an integer number (5443879).

Almost surely, 2^21424237 is an apocalyptic number.

It is an amenable number.

21424237 is a deficient number, since it is larger than the sum of its proper divisors (351279).

21424237 is an equidigital number, since it uses as much as digits as its factorization.

21424237 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 351278.

The product of its digits is 2688, while the sum is 25.

The square root of 21424237 is about 4628.6323033916. The cubic root of 21424237 is about 277.7378832958.

Adding to 21424237 its reverse (73242412), we get a palindrome (94666649).

The spelling of 21424237 in words is "twenty-one million, four hundred twenty-four thousand, two hundred thirty-seven".