21036565 has 32 divisors (see below), whose sum is σ = 29548800. Its totient is φ = 14208000.

The previous prime is 21036563. The next prime is 21036577. The reversal of 21036565 is 56563012.

It is not a de Polignac number, because 21036565 - 2¹ = 21036563 is a prime.

It is an alternating number because its digits alternate between even and odd.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21036563) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 139240 + ... + 139390.

It is an arithmetic number, because the mean of its divisors is an integer number (923400).

Almost surely, 2^21036565 is an apocalyptic number.

It is an amenable number.

21036565 is a deficient number, since it is larger than the sum of its proper divisors (8512235).

21036565 is a wasteful number, since it uses less digits than its factorization.

21036565 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 333.

The product of its (nonzero) digits is 5400, while the sum is 28.

The square root of 21036565 is about 4586.5635283947. The cubic root of 21036565 is about 276.0524518740.

Adding to 21036565 its reverse (56563012), we get a palindrome (77599577).

It can be divided in two parts, 2103 and 6565, that added together give a palindrome (8668).

The spelling of 21036565 in words is "twenty-one million, thirty-six thousand, five hundred sixty-five".