21530565 has 24 divisors (see below), whose sum is σ = 42651648. Its totient is φ = 9842400.

The previous prime is 21530563. The next prime is 21530567. The reversal of 21530565 is 56503512.

It is an interprime number because it is at equal distance from previous prime (21530563) and next prime (21530567).

It is not a de Polignac number, because 21530565 - 2¹ = 21530563 is a prime.

It is a super-3 number, since 3×21530565³ (a number of 23 digits) contains 333 as substring.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21530563) 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 23 ways as a sum of consecutive naturals, for example, 33861 + ... + 34490.

It is an arithmetic number, because the mean of its divisors is an integer number (1777152).

Almost surely, 2^21530565 is an apocalyptic number.

It is an amenable number.

21530565 is a deficient number, since it is larger than the sum of its proper divisors (21121083).

21530565 is a wasteful number, since it uses less digits than its factorization.

21530565 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 68369 (or 68366 counting only the distinct ones).

The product of its (nonzero) digits is 4500, while the sum is 27.

The square root of 21530565 is about 4640.1039859038. The cubic root of 21530565 is about 278.1965942019.

The spelling of 21530565 in words is "twenty-one million, five hundred thirty thousand, five hundred sixty-five".