21243317 has 4 divisors (see below), whose sum is σ = 21353580. Its totient is φ = 21133056.

The previous prime is 21243307. The next prime is 21243331. The reversal of 21243317 is 71334212.

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 8916196 + 12327121 = 2986^2 + 3511^2 .

It is a cyclic number.

It is not a de Polignac number, because 21243317 - 2⁶ = 21243253 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21243292 and 21243301.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21243307) 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, 54842 + ... + 55227.

It is an arithmetic number, because the mean of its divisors is an integer number (5338395).

Almost surely, 2^21243317 is an apocalyptic number.

It is an amenable number.

21243317 is a deficient number, since it is larger than the sum of its proper divisors (110263).

21243317 is a wasteful number, since it uses less digits than its factorization.

21243317 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 110262.

The product of its digits is 1008, while the sum is 23.

The square root of 21243317 is about 4609.0472985206. The cubic root of 21243317 is about 276.9538732943.

Adding to 21243317 its reverse (71334212), we get a palindrome (92577529).

The spelling of 21243317 in words is "twenty-one million, two hundred forty-three thousand, three hundred seventeen".