21456565 has 16 divisors (see below), whose sum is σ = 28047600. Its totient is φ = 15662592.

The previous prime is 21456563. The next prime is 21456577. The reversal of 21456565 is 56565412.

It can be written as a sum of positive squares in 8 ways, for example, as 5948721 + 15507844 = 2439^2 + 3938^2 .

It is a cyclic number.

It is not a de Polignac number, because 21456565 - 2¹ = 21456563 is a prime.

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

21456565 is a modest number, since divided by 6565 gives 2145 as remainder.

It is a self number, because there is not a number n which added to its sum of digits gives 21456565.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21456563) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 3931 + ... + 7639.

It is an arithmetic number, because the mean of its divisors is an integer number (1752975).

Almost surely, 2^21456565 is an apocalyptic number.

It is an amenable number.

21456565 is a deficient number, since it is larger than the sum of its proper divisors (6591035).

21456565 is a wasteful number, since it uses less digits than its factorization.

21456565 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3816.

The product of its digits is 36000, while the sum is 34.

The square root of 21456565 is about 4632.1231633021. The cubic root of 21456565 is about 277.8775101733.

The spelling of 21456565 in words is "twenty-one million, four hundred fifty-six thousand, five hundred sixty-five".