21008065 has 8 divisors (see below), whose sum is σ = 27148968. Its totient is φ = 15513600.

The previous prime is 21008041. The next prime is 21008081. The reversal of 21008065 is 56080012.

It is a happy number.

It can be written as a sum of positive squares in 4 ways, for example, as 1498176 + 19509889 = 1224^2 + 4417^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 21008065 - 2¹¹ = 21006017 is a prime.

It is a Duffinian number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 161536 + ... + 161665.

It is an arithmetic number, because the mean of its divisors is an integer number (3393621).

Almost surely, 2^21008065 is an apocalyptic number.

It is an amenable number.

21008065 is a deficient number, since it is larger than the sum of its proper divisors (6140903).

21008065 is a wasteful number, since it uses less digits than its factorization.

21008065 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 323219.

The product of its (nonzero) digits is 480, while the sum is 22.

The square root of 21008065 is about 4583.4555741275. The cubic root of 21008065 is about 275.9277317264.

Adding to 21008065 its reverse (56080012), we get a palindrome (77088077).

The spelling of 21008065 in words is "twenty-one million, eight thousand, sixty-five".