21240413 has 4 divisors (see below), whose sum is σ = 21600480. Its totient is φ = 20880348.

The previous prime is 21240403. The next prime is 21240433. The reversal of 21240413 is 31404212.

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 21240413 - 2¹² = 21236317 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21240391 and 21240400.

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 3 ways as a sum of consecutive naturals, for example, 179945 + ... + 180062.

It is an arithmetic number, because the mean of its divisors is an integer number (5400120).

Almost surely, 2^21240413 is an apocalyptic number.

It is an amenable number.

21240413 is a deficient number, since it is larger than the sum of its proper divisors (360067).

21240413 is an equidigital number, since it uses as much as digits as its factorization.

21240413 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 360066.

The product of its (nonzero) digits is 192, while the sum is 17.

The square root of 21240413 is about 4608.7322551869. The cubic root of 21240413 is about 276.9412526868.

Adding to 21240413 its reverse (31404212), we get a palindrome (52644625).

The spelling of 21240413 in words is "twenty-one million, two hundred forty thousand, four hundred thirteen".