21540065 has 4 divisors (see below), whose sum is σ = 25848084. Its totient is φ = 17232048.

The previous prime is 21540059. The next prime is 21540083. The reversal of 21540065 is 56004512.

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 15108769 + 6431296 = 3887^2 + 2536^2 .

It is a cyclic number.

It is not a de Polignac number, because 21540065 - 2⁴ = 21540049 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21540065.

It is an unprimeable number.

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, 2154002 + ... + 2154011.

It is an arithmetic number, because the mean of its divisors is an integer number (6462021).

Almost surely, 2^21540065 is an apocalyptic number.

It is an amenable number.

21540065 is a deficient number, since it is larger than the sum of its proper divisors (4308019).

21540065 is an equidigital number, since it uses as much as digits as its factorization.

21540065 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4308018.

The product of its (nonzero) digits is 1200, while the sum is 23.

The square root of 21540065 is about 4641.1275569629. The cubic root of 21540065 is about 278.2375047096.

Adding to 21540065 its reverse (56004512), we get a palindrome (77544577).

The spelling of 21540065 in words is "twenty-one million, five hundred forty thousand, sixty-five".