21240423 has 12 divisors (see below), whose sum is σ = 32295640. Its totient is φ = 13414896.

The previous prime is 21240403. The next prime is 21240433. The reversal of 21240423 is 32404212.

21240423 is a `hidden beast` number, since 2 + 1 + 240 + 423 = 666.

It is not a de Polignac number, because 21240423 - 2⁵ = 21240391 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21240396 and 21240405.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21240403) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 61936 + ... + 62277.

Almost surely, 2^21240423 is an apocalyptic number.

21240423 is a deficient number, since it is larger than the sum of its proper divisors (11055217).

21240423 is a wasteful number, since it uses less digits than its factorization.

21240423 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 124238 (or 124235 counting only the distinct ones).

The product of its (nonzero) digits is 384, while the sum is 18.

The square root of 21240423 is about 4608.7333400838. The cubic root of 21240423 is about 276.9412961482.

Adding to 21240423 its reverse (32404212), we get a palindrome (53644635).

The spelling of 21240423 in words is "twenty-one million, two hundred forty thousand, four hundred twenty-three".