21242565 has 12 divisors (see below), whose sum is σ = 36820524. Its totient is φ = 11329344.

The previous prime is 21242563. The next prime is 21242569. The reversal of 21242565 is 56524212.

It can be written as a sum of positive squares in 2 ways, for example, as 3526884 + 17715681 = 1878^2 + 4209^2 .

It is not a de Polignac number, because 21242565 - 2¹ = 21242563 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21242563) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 235984 + ... + 236073.

It is an arithmetic number, because the mean of its divisors is an integer number (3068377).

Almost surely, 2^21242565 is an apocalyptic number.

It is an amenable number.

21242565 is a deficient number, since it is larger than the sum of its proper divisors (15577959).

21242565 is a wasteful number, since it uses less digits than its factorization.

21242565 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 472068 (or 472065 counting only the distinct ones).

The product of its digits is 4800, while the sum is 27.

The square root of 21242565 is about 4608.9657191175. The cubic root of 21242565 is about 276.9506052584.

Adding to 21242565 its reverse (56524212), we get a palindrome (77766777).

The spelling of 21242565 in words is "twenty-one million, two hundred forty-two thousand, five hundred sixty-five".